Java Methods

Sometimes our program grows in size, and we want to separate the logic of the main method from the other methods.

For instance, if we calculate the average of a number pair 5 times, we can use methods to avoid repeating the logic. [DRY – Don’t Repeat Yourself]

Syntax of a Method

A method is a function written inside a class. Since Java is an object-oriented language, we need to write the method inside some class.

Syntax of a method :

returnType nameOfMethod() {
//Method body
}

The following method returns the sum of two numbers

int mySum(int a, int b) {
	int c = a+b;
	return c;	//Return value
}

In the above method, int is the return data type of the mySum function.

mySum takes two parameters: int a and int b.

The sum of two values integer values(a and b) is stored in another integer value named 'c'.

mySum returns c.

Calling a Method :

A method can be called by creating an object of the class in which the method exists followed by the method call:

Calc obj = new Calc(); //Object Creation

obj.mySum(a , b); //Method call upon an object

The values from the method call (a and b) are copied to the a and b of the function mySum. Thus even if we modify the values a and b inside the method, the values in the main method will not change.

Void return type :

When we don’t want our method to return anything, we use void as the return type.

Static keyword :

The static keyword is used to associate a method of a given class with the class rather than the object.

You can call a static method without creating an instance of the class.

In Java, the main() method is static, so that JVM can call the main() method directly without allocating any extra memory for object creation.

All the objects share the static method in a class.

Process of method invocation in Java :

Consider the method Sum of the calculate class as given in the below code :

class calculate{
     int sum(int a,int b){
        return a+b;
    }

The method is called like this:

class calculate{
     int sum(int a,int b){
        return a+b;
    }

public static void main(String[] args) {
         
        calculate obj = new calculate();
        int c = obj.sum(5,4);
        System.out.println(c);
    }
}

Output

Inside the main() method, we've created an object of the calculate class.

obj is the name of the calculate class.

Then, we've invoked the sum method and passed 5 and 4 as arguments.

Note: In the case of Arrays, the reference is passed. The same is the case for object passing to methods.

Example

package com.company;

public class cwh_31_methods {

    static int logic(int x, int y){
        int z;
        if(x>y){
            z = x+y;
        }
        else {
            z = (x +y) * 5;
        }
        x = 566;
        return z;
    }


    public static void main(String[] args) {
        int a = 5;
        int b = 7;
        int c;
        // Method invocation using Object creation
        //cwh_31_methods obj = new cwh_31_methods();
        //c = obj.logic(a, b);
        c = logic(a, b);
        System.out.println(a + " "+ b);
        int a1 = 2;
        int b1 = 1;
        int c1;
        c1 = logic(a1, b1);
        System.out.println(c);
        System.out.println(c1);
    }
}

Output

5 7
60
3

Conclusion

In this page (written and validated by A. Gawali) you learned about Java Methods . What's Next? If you are interested in completing Java tutorial, your next topic will be learning about: Java Method Overloading.

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