Found 9326 Articles for Object Oriented Programming

Just as you can pass primitive type values to methods, you can also pass arrays to methods. For example, the following method displays the elements in an int array -Examplepublic static void printArray(int[] array) {    for (int i = 0; i < array.length; i++) {       System.out.print(array[i] + " ");    } }You can invoke it by passing an array. For example, the following statement invokes the print Array method to display 3, 1, 2, 6, 4, and 2 -printArray(new int[]{3, 1, 2, 6, 4, 2});

A class, method, constructor, interface, etc. declared public can be accessed from any other class. Therefore, fields, methods, blocks declared inside a public class can be accessed from any class belonging to the Java Universe.However, if the public class we are trying to access is in a different package, then the public class still needs to be imported. Because of class inheritance, all public methods and variables of a class are inherited by its sub classes.ExampleThe following function uses public access control -public static void main(String[] arguments) {    // ... }The main() method of an application has to be ... Read More

Variables, methods, and constructors, which are declared protected in a superclass can be accessed only by the subclasses in other package or any class within the package of the protected members' class.The protected access modifier cannot be applied to class and interfaces. Methods, fields can be declared protected, however methods and fields in a interface cannot be declared protected.Protected access gives the subclass a chance to use the helper method or variable, while preventing a non-related class from trying to use it.ExampleThe following parent class uses protected access control, to allow its child class override openSpeaker() method - class AudioPlayer ... Read More

Default access modifier means we do not explicitly declare an access modifier for a class, field, method, etc.A variable or method declared without any access control modifier is available to any other class in the same package. The fields in an interface are implicitly public static final and the methods in an interface are by default public.ExampleVariables and methods can be declared without any modifiers, as in the following examples -String version = "1.5.1"; boolean processOrder() {    return true; }

Methods, variables, and constructors that are declared private can only be accessed within the declared class itself.Private access modifier is the most restrictive access level. Class and interfaces cannot be private.Variables that are declared private can be accessed outside the class, if public getter methods are present in the class.Using the private modifier is the main way that an object encapsulates itself and hides data from the outside world.ExampleThe following class uses private access control - public class Logger {    private String format;    public String getFormat() {       return this.format;    }    public void setFormat(String ... Read More

Following program creates an array with null values. Convert it a list with not-null values only and then get the array of that list.Exampleimport java.util.ArrayList; import java.util.List; public class Tester { public static void main(String[] args) { String[] array = {"I", null, "love", null, "Java" }; List values = new ArrayList(); for(String data: array) { if(data != null) { values.add(data); } } String[] target = values.toArray(new String[values.size()]); for(String data: target) { System.out.println(data + " "); } } }OutputI love Java

Yes, an array can be returned from a java function. See the example below − Example public class Tester { public static void main(String[] args) { int[] array = getData(); for(int i: array) { System.out.println(i); } } public static int[] getData() { int[] dataArray = {1, 2, 3, 4}; return dataArray; } } Output 1 2 3 4

Following program print the sum of the all the numbers in an array.Examplepublic class Tester {    public static void main(String[] args) {       int[] dataArray = {1, 2, 3, 4};       int sum = 0;       for(int i: dataArray) {          sum += i;       }       System.out.println(sum);    } }Output10

The array is faster in case of access to an element while List is faster in case of adding/deleting an element from the collection.

LinkedList should be used where modifications to a collection are frequent like addition/deletion operations. LinkedList is much faster as compare to ArrayList in such cases. In case of read-only collections or collections which are rarely modified, ArrayList is suitable.