Building java programs 3rd edition pdf free download






















Objects provide abstraction by giving us more powerful pieces of data that have sophisticated behavior without having to manage and manipulate the data directly. Items declared public may be seen and used from any class.

Items declared private may be seen and used only from within their own classes. Objects' fields should be declared private to provide encapsulation, so that external code can't make unwanted direct modifications to the fields' values. To access private fields, create accessor methods that return their values. For example, add a getName method to access the name field of an object. Encapsulation allows you to change a class's internal implementation without changing its external view to clients.

When a class is encapsulated clients cannot directly access its fields, so changing those fields will not disturb client behavior as long as the external view method behavior is consistent. Cohesion is the concept of how well a class's contents go together. You can tell that a class is cohesive when each of its fields stores important state related to the object and each method interacts with that state in some way to produce useful behavior.

Code reuse is the practice of writing a single piece of code and using it many times in different programs and contexts. Inheritance is useful for code reuse because it allows you to write a class that captures common useful code and then extend that class to add more features and behavior to it. Overloading a method involves creating two methods in the same class that have the same name but different parameters. Overriding a method involves creating a new version of an inherited method in a subclass, with identical parameters but new behavior to replace the old.

The this keyword refers to the current object, while the super keyword refers to the current class's superclass. Use the super keyword when calling a method or constructor from the superclass that you've overridden, and use the this keyword when accessing your object's own fields, constructors, and methods.

UndergraduateStudent can call the setAge method but cannot directly access the name or age fields from Student. None of the statements produce errors. An is-a relationship is a subclass relationship such as those created by inheritance. A has-a relationship is when one object contains a reference to another as a field. Having Square extend Rectangle is a poor design because a Square cannot substitute for a Rectangle. If the client thinks the Square is a Rectangle and calls setWidth or setHeight on it, unexpected results will occur.

The client will expect the width and height to be different after the call, but they may not be. Having each of the 52 playing cards in its own class is not a good design because it will result in a clutter of code files without significant differences between them. A better design would have one Card class with fields for rank and suit. We made DividendStock a separate subclass from Stock for two major reasons. First, not all stocks pay dividends, so it does not make sense for every Stock object to have a dividends field and a payDividend method.

Second, the Stock code already worked correctly, so we did not want to tamper with it needlessly. Making DividendStock a separate class constituted an additive and noninvasive change. Extending a class causes your class to inherit all methods and data from that class. Implementing an interface forces you to write your own code to implement all the methods in that interface. The code for class C must contain implementations of the methods m1 and m2 to compile correctly, because C claims to implement the I interface.

What's wrong is that interfaces can't declare fields or write bodies for methods. The following is a correct Colored interface:. The following are the implementations of the method in the Circle , Rectangle , and Triangle classes:. An abstract class is a class intended to be used only as a superclass for inheritance. It's like a normal class in that it can have fields, methods, constructors, and so on.

It's different from a normal class in that it can have abstract methods, which are like methods of an interface because only their headers are given, not their bodies. It's also different from a normal class because it can't be instantiated used to create objects. You can be sure that the OrderedByLength class contains a getElement method and that it implements the arrange method, because if it extends Ordered without being abstract itself, it must have that method in order to compile.

One good design would be to have an abstract superclass named Movie with data such as name, director, and date. There would be subclasses of Movie to represent particular movie types, such as Drama , Comedy , and Documentary.

Each subclass would store its specific data and behavior. An ArrayList is a structure that stores a collection of objects inside itself as elements. Each element is associated with an integer index starting from 0. You should use an ArrayList instead of an array if you don't know how many elements you'll need in advance, or if you plan to add items to or remove items from the middle of your dataset.

Code to declare an ArrayList containing ["It", "was", "a", "stormy", "night"] :. Code to insert two additional elements, "dark" and "and" , at the proper places:.

Code to print out whether or not a list of String s contains the value "IS" , without using a loop:. Code to print out the index at which the list contains the value "stormy" and the index at which it contains "dark" :. A for-each loop that prints the uppercase version of each String in the list on its own line:. The code throws a ConcurrentModificationException because it is illegal to modify the elements of an ArrayList while for-each looping over it.

The code doesn't compile because primitives cannot be specified as type parameters for generic types. The solution is to use the "wrapper" type Integer instead of int.

Change the line declaring the ArrayList to the following:. A wrapper class is one whose main purpose is to act as a bridge between primitive values and objects.

An Integer is an object that holds an int value. Wrappers are useful in that they allow primitive values to be stored into collections. To arrange an ArrayList into sorted order, call the Collections. For example, if your ArrayList is stored in a variable named list , you would call:. A natural ordering is an order for objects of a class where "lesser" objects come before "greater" ones, as determined by a procedure called the class's comparison function.

To give your own class a natural ordering, declare it to implement the Comparable interface and define a comparison function for it by writing an appropriate compareTo method.

Code that reads two names from the console and prints the one that comes first in alphabetical order:. You should use a LinkedList when you plan to add or remove many values at the front or back of the list, or when you plan to make many filtering passes over the list in which you remove certain elements.

The code shown would perform better with an ArrayList , because it calls the get method many times using indexes in the middle and end of the list. This is a slow operation for a LinkedList. An iterator is an object that represents a position within a list and enables you to view or make changes to the elements at that position. Iterators are often used with linked lists because they retain the position in the list, so you don't have to call expensive list methods like get , add , or remove many times on the middle or end of the list.

An abstract data type defines the type of data a collection can hold and the operations it can perform on that data. Linked lists implement the List abstract data type. You should use a Set rather than a List if you wanted to avoid duplicates or wanted to be able to search the collection quickly. You should use a TreeSet when you want to keep the data in sorted natural order.

You should use HashSet s with non- Comparable types or when order doesn't matter, to get the fastest searching time. To do a union, use the addAll method to add one set's contents to the other. To do an intersection, use the retainAll method to remove elements not common to both sets. You can examine every key of a Map by calling the keySet method and then iterating or for-eaching over the keySet.

You can examine every value of a Map by calling the values method and then iterating or for-eaching over that collection of values, or by looking up each associated value using the keys from the keySet. Recursion is a technique where an algorithm is expressed in terms of itself.

A recursive method differs from a regular method in that it contains one or more calls to itself within its body. A base case is a situation where a recursive method does not need to make a recursive call to solve the problem.

A recursive case is a situation where the recursive method does call itself. Recursive methods need both cases because the recursive case is called repeatedly until the base case is reached, stopping the chain of recursive calls.

A call stack is the structure of information about all methods that have currently been called by your program. Recursion produces a tall call stack in which each recursive call is represented. The new code shown would cause infinite recursion, because each recursive call just makes another recursive call and doesn't progress toward the base case.

The version of the pow method shown does not have any base case, so the recursive calls will never stop. The second version of the pow method is more efficient than the first because it requires fewer recursive calls.

Both versions are recursive. The base case if statement has a bug: It should test for numbers less than 10, not greater.

The following is the correct line:. When the parameters needed for recursion don't match those that make sense for the client to pass, use a public method with the signature desired by the client and a private helper method with the signature needed for the recursion.

A fractal is an image that is recursively constructed to contain smaller versions of itself. Recursive methods are useful when drawing fractal images because they can elegantly express the recursive nature of the images. Recursion is an effective way to implement a backtracking algorithm because the memory of decisions and points to go back to are represented by the recursive call stack.

The pattern of "choose, explore, un-choose is elegantly represented by recursive calls for each individual choice. A decision tree is a description of the set of choices that can be made by a recursive backtracking method at any point in the algorithm. Decision tree that would have resulted for Figure If the solution had explored NE first instead of last, the solutions would have been printed in this order:.

There are 64 entries at the second level of the full tree. There are entries at the third level of the full tree. Our algorithm avoids such a huge number of choices by only placing one queen in each column of the board. The 8 Queens explore method stops once it finds one solution to the problem. This is because the code has the following lines around its recursive call:. The code could be modified so that it would find and output every solution to the problem by changing that code to the following:.

You can perform a sequential search over the array using a loop, or you can sort the array using Arrays. Closest value to the number of elements that the binary search algorithm will need to examineon an array of one million integers:. A sequential search must be used on an array of Point objects because they do not implement Comparable. To change the order, you could pass a Comparator that defines a different order.

To make it work, you could pass a Comparator that defines an ordering for Point s. We could easily reverse the order of our LengthComparator by using the built-in method Collections. Binary search requires a sorted dataset because it uses the ordering to jump to the next index.

If the elements are out of order, the search isn't guaranteed to find the target element. A binary search of 60 elements examines at most 6 elements, because log 2 60 when rounded up equals 6.

The algorithm will examine indexes 4, 6, and 5 and will return The algorithm doesn't work properly because the input array isn't sorted. The binary search algorithm will examine the following indexes and return the following values for each search:.

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Paperback edition of this book is also available here on Amazon. Paperback edition of this Java book is also available for purchase on Amazon, here.

Instructors, please note that students have access to all Self-Check solutions, so Self-Check problems should probably not be assigned as graded homework. Solutions to Exercises and Programming Projects are not posted publicly for students to see, so those can be assigned as homework problems if so desired. Supplements, 3rd edition The following supplements are available to all instructors and students using the textbook.



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