Methods in Java

This section contains the detail about the Methods in Java.

Methods in Java

A method is a set of statements gathered together to carry out some operation.

Making a Method :

Given below the general syntax of a method :

modifier returnType methodName(parameters) {
//body;
}

Example :

This example returns the number which has maximum value :

public static int max(int num1, int num2) {
int result;
if (num1 > num2)
result = num1;
else
result = num2;

return result; 
}

Method Calling :

The methods which returns value can be used to pass value to variables :

If the method return type is void then it van be used as statement. For example, the method println returns void. The following call is a statement :

System.out.println("Welcome to Devmanuals!");

Example :

public class TestMethod {
   
   public static void main(String[] args) {
      int a = 5;
      int b = 2;
      int c = max(a, b);
      System.out.println("The maximum between " + a +
                    " and " + b + " is " + c);
}
/** Return the max between two numbers */
public static int max(int num1, int num2) {
   int result;
   if (num1 > num2)
      result = num1;
   else
      result = num2;

   return result; 
}

Output :

Method Overloading :

In java, it is possible that two methods have same name, but their parameter declaration must be different . This is called method overloading.

Example 

public class DemoOverload {
void test() {
System.out.println("No parameters");
}

// Overload test for one integer parameter.
void test(int a) {
System.out.println("a:" + a);
}

// Overload test for two integer parameters
void test(int a, int b) {
System.out.println("a and b :" + a + " " + b);
}
}

class overload {
public static void main(String args[]) {
DemoOverload d = new DemoOverload();
d.test();
d.test(10);
d.test(10, 20);

}
}

Output :

Constructor overloading :

The constructor can be overloaded in java, which is helpful in initializing variables and methods(constructors).

Example :

public class ConstructorOverloading {

   public static void main(String args[]) {
	Rectangle rectangle1 = new Rectangle(2, 4);
	int areaInFirstConstructor = rectangle1.first();
	System.out.println(" The area of a rectangle in first constructor is :"+ areaInFirstConstructor);
	Rectangle rectangle2 = new Rectangle(5);
	int areaInSecondConstructor = rectangle2.second();
	System.out.println(" The area of a rectangle in first constructor is :"+ areaInSecondConstructor);
	Rectangle rectangle3 = new Rectangle(2.0f);
	float areaInThirdConstructor = rectangle3.third();
	System.out.println(" The area of a rectangle in first constructor is :"+ areaInThirdConstructor);
	Rectangle rectangle4 = new Rectangle(3.0f, 2.0f);
	float areaInFourthConstructor = rectangle4.fourth();
	System.out.println(" The area of a rectangle in first constructor is :"+ areaInFourthConstructor);
	}
}
class Rectangle {
	int l, b;
	float p, q;

	public Rectangle(int x, int y) {
		l = x;
		b = y;
	}
   public int first() {
		return (l * b);
	}
   public Rectangle(int x) {
		l = x;
		b = x;
	}
   public int second() {
		return (l * b);
	}
   public Rectangle(float x) {
		p = x;
		q = x;
	}
   public float third() {
		return (p * q);
	}
   public Rectangle(float x, float y) {
		p = x;
		q = y;
	}
   public float fourth() {
		return (p * q);

	}

}

Output :

Passing var-args to methods :

Variable length arguments are known as var-args. The method which takes variable number of arguments is called varargs method . Given below method "vaTest( )" excepts variable length arguments. In the below example it  accepts -1, 3, and 0 arguments. See below example to understand it clearly :

Example :

public class ClassVarargs {

static void vaTest(int v[]) {

System.out.println("Number of args :" + v.length + " 

Contents :");

for (int x : v)

System.out.println(x + " ");

System.out.println();

}



public static void main(String args[]) {

int n1[] = { 10 };

int n2[] = { 1, 2, 3 };

int n3[] = {};



vaTest(n1); // one args

vaTest(n2); // two args

vaTest(n3); // three args

}

}

Example :

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