Java Articles - Page 731 of 745

An abstract method is the one which has no definition and declared abstract. In short, an abstract method contains only method signature without body. To use this method, you need to inherit this method by extending the class and provide the method definition. Example public abstract class Employee{ private String name; private String address; private int number; public abstract double computePay(); }

A native method is the one whose method implementation is done in other languages like c++ and Java. These programs are linked to Java using JNI or JNA interfaces. The difference between normal method and native method is That the native method declaration contains native keyword and, the implementation of the method will be other programming language. Example Tester.java public class Tester { public native int getValue(int i); public static void main(String[] args) { System.loadLibrary("Tester"); System.out.println(new Tester().getValue(2)); ... Read More

A native method in Java is a method whose implementation is written in other languages such as c and c++. The ‘native’ keyword is used before a method to indicate that it is implemented in other language.

Whenever, you want to pass different number of arguments each time you call a method you should use vararg methods. This example creates sumvarargs() method which takes variable no of int numbers as an argument and returns the sum of these arguments as an output. Example Live Demo public class Main { static int sumvarargs(int... intArrays) { int sum, i; sum = 0; for(i = 0; i< intArrays.length; i++) { ... Read More

In Java methods, parameters accept arguments with three dots. These are known as variable arguments.sample(int args …){}If they are used you can pass a different number of arguments each time you call these methods.Examplepublic class Sample {    void demoMethod(String... args) {       for (String arg: args) {          System.out.println(arg);       }    }    public static void main(String args[] ) {       new Sample().demoMethod("ram", "rahim", "robert");       new Sample().demoMethod("krishna", "kasyap")    } }Outputram rahim robert krishna kasyap

Methods which uses variable arguments (varargs, arguments with three dots) are known as variadic functions.ExampleLive Demopublic class Sample {     void demoMethod(String... args) {       for (String arg: args) {          System.out.println(arg);       }     }    public static void main(String args[] ){       new Sample().demoMethod("ram", "rahim", "robert");       new Sample().demoMethod("krishna", "kasyap");    } }Outputram rahim robert krishna kasyap

Annotations are a tag (metadata) which provides info about a program. Annotations in Java Start with the symbol ‘@’. They are used by the compiler to detect errors. Software tools to generate code. They are used to show attributes of an element: e.g. @Deprecated, @Override. Annotation are used to describe the purpose of an element of the framework, e.g. @Entity, @TestCase, @WebService Annotations describe the behaviour of an element: @Statefull, @Transaction. Example Live Demo class Sample{ public void display(){ System.out.println(" "); } } public ... Read More

In Aggregation relationship among classes by which a class (object) can be made up of any combination of objects of other classes. It allows objects to be placed directly within the body of other classes.A composition is also a type of aggregation where the relationship is restrictive i.e. If two objects are in composition, the composed object will not exist without the other.

VM first looks for the main method (at least the latest versions) and then, starts executing the program including static block. Therefore, you cannot execute a static block without main method. Example public class Sample { static { System.out.println("Hello how are you"); } } Since the above program doesn’t have a main method, If you compile and execute it you will get an error message. C:\Sample>javac StaticBlockExample.java C:\Sample>java StaticBlockExample Error: Main method not found in class StaticBlockExample, please define the main method as: public static ... Read More

The java.io.PrintStream.println() method prints an array of characters and then terminate the line. This method behaves as though it invokes print(char[]) and then println(). Using this method you can print the data on the console. import java.io.*; public class PrintStreamDemo { public static void main(String[] args) { char[] c = {'a', 'b', 'c'}; // create print stream object PrintStream ps = new PrintStream(System.out); // print an array and change line ps.println(c); ps.print("New Line"); // flush the stream ps.flush(); } } Output abc New Line