SCHAUM'S OUTLINE OFDATA STRUCTURES WITH JAVA Second Edition JOHN The material in this eBook also appears in the print version of this Arrays Class 29 The Sequential Search Algorithm 30 The Binary Search. Data Structures with c - By Schaum series. Ar if. Loading Preview. Sorry, preview is currently unavailable. You can download the paper by clicking the button. Data Structures With c - By Schaum Series - Free ebook download as PDF File . pdf) or Data Structures and Algorithms Made Easy-Narasimha Karumanchi.

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Data Structures With C - By Schaum Lipschutz - Ebook download as PDF File . pdf) or view presentation slides Data Structure Schaum Series (Chapter 4 to 9) by Gitansh Data Structures and Algorithms Made Easy-Narasimha Karumanchi . Providing Important topics YouTube links for Data Structure and Algorithms” What is Dynamic Programming Bellman-Ford Algorithm-Single Source Shortest Path | Dynamic Programming . As of today we have 78,, eBooks for you to download for free. The study of data structures and algorithms is fundamental to computer into this course.

Are you trying to find a source that gives you concise explanations of core concepts? Don't get me wrong: It's quite comprehensive and covers a lot of topics. It provides excellent examples and many exercises are given and solved for you. The book is written in a clear manner also. However, this is intended as a "refresher": As you can image, each topic is given 3 lines, and then an example is provided.

If you decided to pick this book up because you dont want to go through your long texbtook , and you are short on time, put it back. This isn't the right choice - this is more of a review book. I love how this book goes over in detail about what data structures mean in Java and the exercises it has to practice that understanding.

Recommended for anyone who wants to do a lot of practice on the subject. The sample codes and mainly the java generic session or any session that uses generic types that teach parameterized types are very difficult to understand due to the missing symbols. It is not only missing this symbol but the whole generic declaration in classes and in parameters type. I had to search in the internet for a tutorial on Java generic types.

I am still reading this book. Theory discussions and also practices were excellent so far and I really appreciate the author and Schaum's itself to provide CS students such a great fundamental material. Thanks much! See all 7 reviews.

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PillPack Pharmacy Simplified. site Renewed Refurbished products with a warranty. site Second Chance Pass it on, trade it in, give it a second life. So an array with elements would take twice as long to process: So an array with 1,, elements would also take about 2 ms to process. But if you want to maintain an ordered list that allows quick insertions and deletions, you should use a linked data structure.

This chapter shows how to do that. This suggests that we should keep our arrays in sorted order. But inserting new elements in an ordered array is difficult. The main problem is that we have to shift all the larger elements forward to make room for the new element to be placed in its correct ordered position.

This can be done by the insert method shown in Example 3. The code at lines 4—7 searches the array for the correct position for x to be inserted. The arraycopy method is a static method in the System class.

It is usually the most efficient way to copy elements between arrays or within a single array. Its five arguments are: Finally, x is inserted into a[i] at line 9, as shown in Figure 3. Figure 3. So this is a 4 n operation. Deleting an element is simply the reverse of the insertion process. So deletion is also a 4 n operation. This solution requires more space a second array and makes the code a bit more complicated.

But it eliminates the need to move the elements. It allows the elements to be stored at an arbitrary position in the array, using the auxiliary index array to locate them for ordered access.

The main idea is shown in Figure 3. So if we save the order of the index numbers 3, 5, 1, 4, 6 , then we can access the elements in order: An index array is an array whose elements are index values for another array. By storing the index numbers 3, 5, 1, 4, 6 in an index array k[] shown in Figure 3. The reason we wanted to allow the element to be stored in arbitrary positions in the first place was to simplify the insertion and deletion operations.

We wanted to avoid having to shift segments of a[] back and forth. But the solution shown in Figure 3. If we had to insert the element 50, we could put it at position a[0] or a[2] or any place after a[6], but we would then have to insert its index into the index array k[] between k[2] and k[3] to keep track of the order of the elements.

A better solution is to use the same array positions in the index array k[] as we are using in the data array a[]. Since the index array is keeping track of the correct order of the index numbers of the data elements, it can be used to do the same for the index numbers themselves. The starting index 3 is stored in k[0].

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That begins the chain of indexes: The index 0 signals the end of the ordered sequence. The index sequence 0, 3, 5, 1, 4, 6 gives us the data elements in order: The extra variable free, shown Figure 3. The value 7 means that k[7] and a[7] should be used next.

The implementation of an index array solves the problem of having to shift segments of array elements back and forth during deletions and insertions. Then just follow these three steps: This improves the insert method shown in Example 3.

At line 6, x is inserted in the next free location in the array a[]. At line 7, the index of the next location after x is stored in k[free]. At line 8, the index of x is copied into k[i], and then free is incremented to the index of the next free location.

In practice, we would probably include a resize method. Their relative positions in the index array match the positions of the corresponding data elements. So we can combine them into a single array of data-address pairs, as shown in Figure 3. Fortunately, Java allows an even better solution, one that allows us to eliminate both arrays! Taking an object-oriented point of view, we see in Figure 3.

Each object contains a data element and the address of the next object in the sequence. In Java, objects are directly accessed by their addresses. Here, the arrows represent object references i. The Java runtime system does all the rest of the bookkeeping. The code is given in Example 3. Its next field is declared to have type Node.

Each Node object contains a field that is a reference to a Node object. The other field in the Node class is its data field, declared at line 2 here to be an int. Of course in general this field could be any type we want whatever type values we have to store in the list.

The Node class in Example 3. Note that, since we have explicitly defined a constructor that takes at least one argument, the compiler will not implicitly define a no-argument constructor. Therefore, since we have not explicitly defined a no-argument constructor, none will exist.

That means that the only way a Node object can be created is with the one-argument constructor at line 5 ; that is, we must provide a data value for each new Node object that we create.

Its data field contains the integer 22, and its next field contains a reference to another Node object not shown. Although it is common to use an arrow like this to represent an object reference, it is good to keep in mind that the actual value of the reference is the memory address of the object to which it refers. In other programming languages, such variables are called pointers; hence their common depiction as arrows.

Recall that in Java each reference variable either locates an object or is null. The value null means that the variable does not refer to any object. The memory address that is stored in a null reference variable is 0x0 the hexadecimal value 0 ; no Figure 3.

Example 3. The result is shown in Figure 3. Note that the start variable is merely a reference to the Node object. Also note that the next reference in the Node object is null, indicated by the black dot with no arrow emanating from it.

In Java, every class field that is an object reference i. In the figures that follow, each Node object is shown as a box with two parts: This simply abbreviates the versions shown in Figure 3. Continuing the code in Example 3. Now the list has two nodes, as shown in Figure 3. To do that, we have to assign it to the next field of the node that contains But the only node to which we have external access i.

Its name is start. So we have to use the expression start. Similarly, the fourth node is added at line 4 using the expression start. That finally gives us the five-node list shown in Figure 3. The code in Example 3. Obviously, if we wanted to build a linked list of 50 nodes, this approach would be unworkable.

Since it will refer to individual nodes, it should be declared to be a Node reference, like this: Node p; And since our only access to the nodes is from the start node, we should initialize p like this: This same assignment can thus be executed as many times as is needed to advance through the linked list. But one big advange is that it is easily managed within a loop.

For example, the same list can be built with the three lines of code in Example 3. Each step in the execution of this code is shown in Figure 3. The reference variable p is analogous to an array index i: It advances through the nodes of a linked list just as i advances through the elements of an array. Consequently, it is natural to use p in a for loop, just as we would use the array index i. For example, compare Example 3. Then the for loop at lines 5—7 constructs the other four nodes.

The second for loop at lines 8—10 prints the node data in the first five lines of output. The third for loop at lines 11—13 gives the actual memory addresses of the five Node objects. When you use an object reference like p in a string expression such as System. Unless it has been overridden, the version of the toString method that is defined in the Object class will execute, as it did in the program in Example 3. So the last five lines of output report that the five Node objects are stored at the hexadecimal memory addresses 0xc1, 0x3f5d07, 0xf4a24a, 0xcac, and 0xa These then are the actual values stored in the reference variables start, start.

You can see from Figure 3. Showing the actual memory address values instead requires more effort to see which node references which. Moreover, those memory address values are runtime dependent: They will be different on different computers, and maybe even on the same computer at different times. One final note: When i is 1, that evaluates to 33; when i is 4, it evaluates to After the value is obtained, it is passed to the Node class constructor at line 5 of Example 3.

That constructs a node with that value in its data field and null in its next field. The constructor returns a reference to the Node object. It is that reference that is assigned first to p.

The key is that the assignments are made from right to left. So we know that p is not updated until after its next field is. So, first the next field is set to point to the new node, and then the loop control variable p is advanced to that next node.

To simplify the process, we add a two-argument constructor to our Node class, as shown in Example 3. This allows us to create the node and insert it all at once. It shows next as a reference to a Node object and x as an int with value Passing these two arguments to the constructor creates a new Node object that contains 50 and whose next field points to the same object that the given next pointer points to.

The constructor then returns a reference to the new Node object, which is assigned to q. To appreciate its simplicity, compare it with the equivalent method in Example 3.

The variable p is declared at line 4 to be a reference to Node objects. It is initialized to point to the start node, which contains 22 in Figure 3. The loop control condition p. But inside the loop, at line 6, the condition will stop the loop prematurely, before p reaches any nodes that should come after the new node. This is how the list remains in ascending order: New elements are always inserted between the elements that are less than it and those that are greater than it.

On each iteration of the while loop, this assignment moves p to point to the next node in the list. The actual insertion is done by the statement at line 9. The expression new Node x,p. The statement at line 7 assigns it to p. This changes the next pointer of the p node the node containing At that point, p. Once we understand this process, we might as well use the power of Java and write it in the single statement p.

To see why that precondition is needed, look at what the method would do if x were 20 instead of In that case, the break condition at line 6 would be true on the first iteration of the while loop, leaving p pointing at the start node when the new node gets inserted at line 9.

The result, as shown in Figure 3. The problem is that we lack a node to precede the new one. This uses a little extra space, but it allows the insert method in Example 3. The other solution is to modify the insert method in Example 3.

This is done in Example 3.

There are two situations in which the insert should be done at the front of the list: Both conditions are handled at line 4. In the first case, we could simply reset start to a new node containing x, like this: In the second case, we also have to assign the new node to start, but we also have to connect it to the rest of the list.

But the only reference we have to the beginning of the list is start itself, so we would have to hold that reference in a temporary variable before reassigning start to the new node. Note that unlike the simpler version in Example 3. The same is true for deletion. Like the insert method, the delete method has two main parts: It also handles the special case at the front of the list separately. Also, if the first element is greater than x, then since the list is sorted, all the elements must be greater than x, so x is not in the list.

Both of 1 2 these cases are handled first at line 5. If the first element in the list equals x, then it is deleted at line 8. This is done by returning start. If it finds one greater, then the method breaks at line 12 and returns without changing the list.

If it finds an element equal to x, then it deletes it at line This is illustrated in Figure 3. A class that is a member of another class is called a nested class.

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This is an important example of the information hiding principle that we have applied in other contexts. If X is any type class or interface and Y is any other type nested within X, then every member of X is accessible from Y and every member of Y is accessible from X.

This is illustrated in Example 3. The Main class in Example 3. Both classes have a private int field. Main declares and initializes m at line 2; Nested declares and initializes n at line The Nested class also defines a private method f at line Outside of Nested; nested. That instantiates the Nested class at line 5. The private field n of the Nested class is accessed at line 6, and the private method f of the Nested class is accessed at line 7.

This shows that private members of a nested class are accessible from its enclosing class. Symmetrically, the private members of the enclosing class are accessible from within its nested class, as demonstrated by line The UML symbol for the nesting of one class inside another uses a circle with a plus sign inside in place of the arrowhead, as shown in Figure 3.

Since all members of a Figure 3. Normally, a nested class should be declared static unless its instances need to access nonstatic members of its enclosing class. A nested class that is nonstatic is called an inner class. The Node class defined in Example 3.

So it should be nested inside its List class. Moreover, since nodes have no need to access List methods or fields, the Node class should be declared as a static nested class. This is done at line 12 in Example 3. A developer could change the implementation without having to modify any code outside of that class. Problems 3. Changing one list should have no effect upon the other.

Note that the two lists must be completely independent of each other. Note that no new nodes are created by this method. Note that the three lists should be completely independent of each other. Changing one list should have no effect upon the others. Answers to Review Questions 3. To find the th element, you have to move sequentially through the first 99 elements.

Its main purpose is to provide a unified framework for implementing common data structures so that the resulting classes can be used in a consistent, efficient, and intuitive manner. This chapter outlines how these types can be used. The JCF specifies four general types of collections: List, Queue, Set, and Map. These are defined as interfaces and are extended and implemented with other interfaces and classes in the java. The relationships among the main classes and interfaces in the JCF are summarized in Figure 4.

The interfaces are shown on the right in italics, and the classes that implement them are on their left. The dashed lines indicate direct implementation. Inheritance, both between classes and between interfaces is shown by solid lines. For example, the AbstractList class extends the AbstractCollection class, and the List interface extends the Collection interface. Note that some of the class names have the prefix Abstract, which indicates that they include abstract methods that are implemented by their subclasses.

A list is a sequence of elements. A queue is a first-in-first-out collection, like a waiting line. A set is an unstructured collection of distinct elements. These are more specialized types.

A Deque is a doubleended queue, allowing insertions and deletions at both ends. The SortedSet and SortedMap interfaces work only with objects that can be compared, like strings. The JCF implements the interfaces with several different data structures.

The simplest structure is an indexed structure, that is, an array, which is used by the ArrayList, the ArrayDeque, the HashSet, and the HashMap classes. Other implementations use a linked structure. The specialized EnumSet and EnumMap classes use a bit string. These twelve implementations are summarized in Table 4. They are the Vector, Stack, Dictionary, and Hashtable classes. It specifies 15 methods, as shown in the Javadoc page in Figure 4. Some of these methods are obvious: The equals and hashCode methods are inherited from the Object class and are meant to be overridden.

The add method may work differently for different implementations. For collections that prohibit duplicate elements, this method should add the specified object only if it is not already an element. For collections that allow duplicate elements, the method should add the specified CHAP. Collection interface object, possibly as a duplicate. In either case, the method should return true if and only if it changed the collection.

For example, if an implement prohibits null elements, then the method should throw a NullPointerException if the argument is null. In that case, it would implement the method like this: Note the parameter specifier: The containsAll method is to the addAll method as the contains method is to the add method. In particular, it should return true if invoked immediately after a call to the addAll method with the same Collection argument.

The iterator method returns an Iterator object that is bound to its implicit argument. Iterators are outlined on page The Collection interface specifies three optional removal methods.

The remove method deletes one instance of its specified object, if it is an element. The removeAll method deletes all the elements that are equal to elements in its specified collection. The retainAll method deletes all the elements that are not equal to elements in its specified collection.

Note that the addAll , the retainAll , and the removeAll methods are equivalent to the set-theoretic union, intersection, and complement operators, respectively. These are illustrated in Figure 4. Figure 4. The array returned by the no-argument version has type Object[]. The array returned by the oneargument version has the same array type as the argument. The Collection interface can be used directly as a specification for a Bag class. A bag is an unordered collection that allows duplicate elements.

Its instances represent ordinary sets of unique elements no duplicates. In fact, a set can be defined simply as a collection of unique elements. It extends the AbstractSet class.

That class implements the Set interface, which extends the Collection interface. See Figure 4. The AbstractSet class implements the equals method, the hashCode method, and the removeAll method, designating the other 12 methods as abstract. This means that the concrete EnumSet, HashSet, and TreeSet classes have their own specialized implementations of those 12 methods. The HashSet class gets its name from the fact that collections of this type maintain no order among their elements; they are all mixed up, like hash.

The isEmpty method is tested at line 4 and again at line At line 5, the collection is loaded with five elements. This is done by the static addAll method defined in the java. Collections class. Note that the order with which the five elements are printed at line 6 is different from the order with which they were added to the set.

The size and contains methods are tested at lines 7—9.

The add method is tested at line 11, and the remove method is tested at line At line 15, the one-argument toArray method is used to generate a String array of the same elements that are in the collection. The for loop at lines 16—18 confirms that the array contains the same elements. Lines 20—21 create and load a second set, named g8. This is then used together with the set collection to test the retainAll , removeAll , and addAll methods at lines 23— Finally, the clear method is tested at line Specifying the element type this way causes the compiler to prevent any non-String objects from being inserted into the collection, making it type-safe.

The JCF uses type parameters in most of its classes and interfaces. Whatever type that is, it must also be the type for the parameter o in the offer method at line 2 and the return type for the other four methods specified at lines 3—6. Like a method parameter, it stands for a type that can be substituted for it. The actual type that is substituted for the type parameter is called a type argument. For example: DEC, 25 ; System. It has two type parameters: S and T.

In the code at lines 14, 15, 17, 22, and 26, these two type parameters are used as place holders for actual types. But the construct is required when the constructor is invoked, as at line 3. Recompile with Xlint: You can avoid that simply by specifying an element type; even Object itself, like this: This allows the type parameter E to be used in place of an actual type in the method block at line 8.

Note that if we used Collection instead of Collection at line 1, then the method would only apply to collections whose element type is specified as Object.

For example, if you wanted to restrict the print method in Example 4. It acts like a finger, pointing to one element at a time, much like the cursor of a text editor points to one character at a time. And like a cursor, an iterator has the capability of moving from one element to the next and of deleting its current element. The analogy between iterators and cursors is not complete. Most iterators cannot jump around the way cursors can. On the other hand, it is possible to have several independent iterators traversing the same collection.

Moreover, it is possible to have several different iterator classes defined for the same collection class, each with its own traversal algorithms. The requirements for an iterator are specified in the java. Iterator interface, shown in Figure 4. Iterator interface The next method returns the current element of the collection to which the iterator is bound.

Each time the next method is invoked, it advances the iterator to the next element in the collection. The hasNext method returns true unless the iterator has reached the end of its traversal. This predicate is used to determine whether the next method can be called again. The remove method deletes the last element returned by the next method.

This means that next must be called before each call to remove , designating the element to be deleted.

It returns a new iterator, bound to the collection and initialized to its first element. MZ it1. BR it1. PT it1. CV The Iterator object it1 is instantiated at line 6 and returned by the iterator method. Bound to the port collection, it visits the elements in the same order as they were printed at line 5.

Note that this order is not the same as the order in which the elements were added to the collection. Since the collection is a set, its elements have no intrinsic order. It is the iterator itself that computes the traversal sequence.

You can see from the output from line 5 that the toString method invoked implicitly by the println method uses the same traversal sequence, obviously using its own iterator to build the string. At line 11, the last next call was at line 10, which returned the MO element; so MO is deleted by remove at line Similarly, at line 14, the last next call was at line 13, which returned the GW element; so GW is deleted by remove at line These deletions are evident from the output produced by the while loop at lines 17— Notice that that loop uses the independent iterator it2 to traverse the collection.

Note that the code at lines 16—19 make a complete traversal of the collection. This is guaranteed by the instantiation of the new iterator at line 16 and the use of the hasNext method to control the loop. The last output, generated at line 21, confirms that the two iterators it1 and it2 are independent.

The action of it2 had no effect on it1, which returns the CV element at line Iterators can be used in a for loop the same way: Thus, the program in Example 4. The declared variable country takes the place of the expression it. The essential feature is that the iterator locates one element at a time in the collection. These additional 19 methods require implementing classes to maintain an ordering mechanism among their elements, allowing them to be compared for size.

In Java, there are two ways for objects to be compared: Classes whose objects enjoy a natural order implement the comparable interface. These include the wrapper classes Integer, Double, etc. User-defined orderings can be defined for a class by implementing the Comparator interface, which is part of the JCF.

SortedSet interface how its two arguments are ordered: As a result, the SortedSet collection orders its elements by applying alphabetical ordering to their reversed strings. GB engl. ZA engl. IN engl. NG The set engl is instantiated as a TreeSet of String elements at line 3 and loaded with seven elements at line 4.

An eighth element is added at line 6. The outputs from lines 5 and 7 confirm that the TreeSet is maintaining its elements in their natural alphabetical order. Lines 8—13 illustrate some of the specialized methods implemented by the TreeSet class. The headSet method returns the sorted subset of all elements that precede its argument.

The subSet method returns the sorted subset of elements that begin with its first argument and precede its second argument. The tailSet method returns the sorted subset of all elements that do not precede its argument.

The intrinsic difference between the HashSet and TreeSet classes is their backing data structure. The TreeSet class uses a balanced binary search tree outlined in Chapter 12 to store its elements.

The advantages and disadvantages of these two data structures are summarized in Table 4. These relative advantages and disadvantages make the choice easy: Search tree Elements are accessible in their natural order Access time is proportional to logn Table 4. In practice, the slower access time of the TreeSet class is usually not noticeable, unless the set is really large. The output from line 5 confirms that its access order matches the order in which the elements were inserted.

The output from line 9 shows that the add method inserts at the end of the linked list. In addition to the 15 methods required by the Set interface, the EnumSet class also implements the 13 additional methods specified in its Javadoc page, shown in Figure 4.

Notice that each of these methods returns an EnumSet object, and every one except clone is a static method. These are used to instantiate the sets, like this: MON, Day. SUN, Day. MAR, Month. JUN ; System. SEP, Month. APR, Month. JUN, Month. NOV, Month. FEB ; System.

Variables of that type can have only those 12 specified values or null. At line 7, the EnumSet spring is instantiated by invoking the static range method of the EnumSet class. These work as described in the Javadoc, shown in Figure 4. The addAll method is tested at line 13, producing the union of the shortMonths and spring sets. List elements are usually numbered in sequence: The numbers are called indexes or subscripts. Unlike sets, list data structures usually allow duplicate elements.

The List interface extends the Collection interface. In addition to the 15 methods specified by the Collection interface Figure 4. The indexed addAll method has a second parameter with this generic type: Collection The? The expression? When the array becomes full, the add method resizes it by replacing it with one that is twice as big. That is timeconsuming, but it happens infrequently.

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The array index allows the get and set methods to run in constant time, independent of the size of the collection. Also, the no-argument add method runs in amortized constant time, which means that the time it takes to insert n elements is on average proportional to n. It does so by appending the new elements to the end of the list. The indexed add and remove methods have to shift subsequences of elements back and forth in the array to accommodate the inserted elements and to fill the gaps left by the deleted elements.

Consequently, these operations run in linear time, which means that the time is on average proportional to the size of the collection. The Vector class is similar to the ArrayList class, using a resizable array to store its elements.

It has 45 methods, including the 3 that it inherits from the AbstractList class. In addition to those 3, the 15 methods specified by the Collection interface Figure 4. Most of them are redundant. For example, the removeElement Object method is the same as the remove Object method specified by the Collection interface, and the removeElementAt int method is the same as the remove int method specified by the List interface.

In addition to the 25 methods specified by the Collection and List interfaces, this class also implements these 11 other methods: For example, the call list. Note that the three remove methods listed here are all obviated by the remove int method specified by the List interface.

The LinkedList methods remove and removeFirst are the same as the List method remove 0. The other five new methods element , offer , peek , poll , and remove are outlined below. These extra methods require ListIterator objects to be bidirectional. Thus, previous , hasPrevious , and previousIndex act the same way as next , hasNext ,and nextIndex , respectively, except in the reverse direction.

To avoid implementing the method, the class can simply throw a new UnsupportedOperationException object, as shown on page In computing, a queue is a linear data structure that allows insertions only at one end and deletions only at the other end. As a dynamic data structure, this embodies the first-in-first-out FIFO protocol. The most familiar use of the queue data structure is a print queue, which temporarily holds print jobs for a printer.

The add and offer methods insert the specified element at the back of the queue. The only difference between them is their behavior when the queue is full: The element and peek methods return the element at the front of the queue. The only difference between them is their behavior when the queue is empty: ListIterator interface The remove and poll methods delete and return the element at the front of the queue.

The AbstractQueue class implements 5 of the 20 required methods of the Queue interface: The purpose of this class as with all abstract classes is to serve as a partial implementation, to be completed in a concrete extension by implementing the other required methods.

The Javadoc for the AbstractQueue class states: Queue interface System. This is called composition of classes; a LinkedQueue object is composed of a LinkedList object. Thus, offer uses list. The action of the main method illustrates the FIFO nature of a queue: Insert elements at the back and remove them from the front.

Thus, the first in AR was the first out at line 6 , and the second in BO was the second out at line Instead of removing the element that has been in the queue the longest, it removes the element that has the highest priority. This of course, requires its elements to be prioritized. In other words, the elements have to have some ordering mechanism; either a natural order, such as alphabetic order for strings, or an order imposed by a Comparator object.

That is because the PriorityQueue class is implemented with a heap data structure, which uses an array to store its elements. See Chapter Consequently, the remove method always removes the element that comes first alphabetically.

The Deque interface extends the Queue interface. In addition to the 15 methods specified by the Collection interface and the 5 more methods specified by the Queue interface, the Deque interface specifies these 17 methods: The descendingIterator method is the same as the iterator method, except that it moves in the opposite direction.

They are the traditional names for the insert and delete methods for a stack data structure, which is a deque that allows access at only one end. See Chapter 5. The ArrayDeque class implements the Deque interface by using a resizable array to store its elements.

A key is a unique element that acts as an identifier for its value, which is an element that typically holds several components of data. These data could be the fields of a Country object, using the Country class defined in Example 4. The Map interface is defined like this: The Map interface is shown in Figure 4. It specifies 14 methods. Note that this interface does not extend the Collection interface. Sets, lists, and queues are collections of individual elements, which are not key-value pairs.

The two subinterfaces and five implementing classes of the Map interface are analogous to the corresponding subinterfaces and implementing classes of the Set interface. Like the AbstractSet class, the AbstractMap class implements only those methods that are either independent of the underlying data structure or can be implemented using the other methods.

The EnumMap class is defined like this: AT, new Country "Austria","German",,, PL, new Country "Poland","Polish",,, FR, new Country "France","French",,, Map interface CHAP. Polish, , , EuCodes at lines 13—15, and Country at lines 17— These are the type arguments for the type parameters K and V at line 3.

Three key-value pairs are inserted at lines 3—6. The size , keySet , and get methods are tested at lines 7—9. The get method illustrates the look-up table nature of a map: PL and returns it as: Their distinctions are the same as the distinctions among the corresponding four extensions of the AbstractSet class.

The HashMap class allows any class to be the key type. Its LinkedHashMap extension maintains a doubly linked list of all its elements, allowing ordered key access according the order of insertion.

Arrays class contains static methods for processing arrays, including methods for converting arrays to collections and vice versa. The class is briefly outlined on page Most of the methods in the Arrays class are overloaded with separate versions for the generic array type T[] and for each of the nine specific array types: In addition, most of these have a separate version for a subarray. For example, here are the 18 overloaded versions of the sort method: The eight different method categories are: Collections class provides over 50 static utility methods that implement algorithms for sorting, searching, shuffling, and maintaining collections, among other tasks.

At line 6, the "JP" and "GB" elements are swapped, and then the list is sorted at line 8. At line 10, the binarySearch method searches for the string "CN". The negative output signals that it is not there. The value of k tells where to insert it to keep the list sorted: Finally, at line 16, the reverse method reverses the entire list.

It will also be unwrapped when extracted. This is illustrated in Example 4. At line 10, the element at index 2, which is the Integer object that holds the primitive int value 44, is accessed by the get method. The remove method is overloaded in the JCF: These two versions are invoked at lines 12 and At line 12, the element at index 2, which is the object that holds 44, is removed. At line 15, the element that equals the object that holds 66 is removed. Note that this would not work: This suggests that the alternative, System.

Review Questions 4. Problems 4. ArrayList class. As a member of the Java Collections Framework, it supports all the methods of the Collection interface. As an indexed structure, it provides direct access to its elements by their index numbers.

LinkedList class. As a linked structure, it allows elements to be added and removed in constant time, independent of the size of the list. An iterator provides only sequential access. Arrays class includes an asList method that returns a List object whose elements are the same as those in the array passed to it. See Example 4. Collections class includes an addAll method that adds all elements that are passed to it.

The method takes a variable number of arguments i. When applied, an actual class or interface name must be substituted for the parameter. Solutions to Problems 4. This means that the only accessible object in the collection is the last one that was inserted. A stack of books is a good analogy: Add an element onto the top of the stack. Access the current element on the top of the stack. Remove the current element on the top of the stack.

These three operations are usually named push, peek, and pop, respectively. ES stack. It stands for the deferred element type for the stack.

In addition to the three required stack operations, this interface also specifies an isEmpty method and a size method. The simplest is an indexed implementation, using an ordinary array. Thus, the type parameter E is used wherever the element type has to be specified. For example, at line 29, the local variable element is declared to have type E.

It is declared at line 2 to have type E[], that is, an array of elements of type E. The other class field is the integer size, which keeps a count of the number of elements in the stack. This is used only to specify the initial size of the backing array at line 7. The choice of is arbitrary; any reasonably small positive integer would suffice. Notice how arrays are allocated in a generic collection: Instead, we have to allocate the backing array as an array of Object elements, and then cast that array with E[] in order to assign it to the elements field, which has type E[].

This subterfuge may generate a compiler warning, which can be ignored. The implementations of the five methods required by the Stack interface are pretty straightforward. The size method at line 41 is an accessor method that simply returns the value of the size field.

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The isEmpty method at line 14 returns true or false according to whether or not the value of size is 0. The peek method at line 18 throws an exception if the stack is empty.

Otherwise, it returns the top element on the stack: The pop method at line 25 is almost the same as the peek method. But before returning the top element, it must remove it by decrementing the size field at line 29 and replacing the top element with null at line This last step is done so that no references will be left to an inaccessible object.

The push method at line 34 is essentially the reverse of the pop method. At line 38, the element is added to the array at the next available position, at elements[size], and then the size counter is postdecremented.

If the array is full, then the size counter will equal elements. If that condition holds when push is called, the array is doubled by a call to the private resize method at line This creates the temporary array a[] at line 47, copies all the elements into it at line 48, and then assigns the elements field to it at line Note the use of the assert statement at line Of course, that should never happen, because the resize method is private, and the only place where it is called within this class is at line 36, inside the if block for that same condition.

The ArrayStack class implemented in Example 5. The push , peek , and pop calls should work the same way. The println calls cannot be executed for the ArrayStack class because it has no toString method.It is invoked at line 4 to initialize the ZERO object.

Polynomial toString: Recall that in Java each reference variable either locates an object or is null. The push method at line 34 is essentially the reverse of the pop method. The Node class in Example 3.