Java Methods, Recursion and Method Overloading

What is a method?

A method is a block of code which only runs when it is called. Methods are used to perform certain actions, and they are also known as functions.

Method creation

A method must be declared within a class and defined with the name of the method, followed by parentheses ().

Types of Java methods

There are two types of methods in Java.

Standard Library Methods: The standard library methods are built-in methods in Java that are readily available for use.
User-defined Methods: User-defined methods can create our own choice to perform some task.

Syntax for declaring a method

public class MyClass {
   static void myMethod() {
    // code to be executed
  }
}

myMethod() is the name of the method
static means method belongs to the MyClass class and not an object of the MyClass class.
void means that this method does not have a return value.

Method calling

To call a method in Java, write the method's name followed by two parentheses () and a semicolon;
Example

public class MyClass {
   static void myMethod() {
    System.out.println("Function execution!");
  }
   public static void main(String[] args) {
    myMethod();
  }
}

Output

Function execution!

Method Parameters and Arguments

Parameters act as variables inside the method and information can be passed to methods as parameter.
Example-1 of SI calculation

import java.util.Scanner;
public class MyClass {
   public static int myMethod(int m, int n, int p) {
     return (m*n*p)/100;
   }
   public static void main(String[] args) {
    Scanner obj=new Scanner(System.in);
    System.out.println("Enter value of p,r and t");
    int p=obj.nextInt();
   int r=obj.nextInt();
   int t=obj.nextInt();
   int si=myMethod(p,r,t);
   System.out.println("SI="+si);
  }
}

Output

   Enter value of p,r and t
   5000
   4
   2
   SI=400

Example-2 of SI calculation

import java.util.Scanner;
public class MyClass {
   public static void main(String[] args) {
    Scanner obj=new Scanner(System.in);
    System.out.println("Enter value of p,r and t");
    int p=obj.nextInt();
   int r=obj.nextInt();
   int t=obj.nextInt();
   int si=myMethod(p,r,t);
   System.out.println("SI="+si);
  }
   public static int myMethod(int m, int n, int p) {
     return (m*n*p)/100;
   }
}

Output

   Enter value of p,r and t
   5000
   4
   2
   SI=400

Java Method Overloading

Multiple methods can have the same name with different parameters is called method overloading.
Example

import java.util.Scanner;
public class MyClass {
   static int sum(int x, int y) {
     return x + y;
   }
   static double sum(double x, double y) {
     return x + y;
   }
   public static void main(String[] args) {
   int n1 = sum(7, 5);
   double n2 = sum(5.26, 6.30);
   System.out.println("int: " + n1);
   System.out.println("double: " + n2);
  }
}

Output

int: 12
double: 11.559999999999999

Java Recursion

Recursion is the mechanism of making a function call itself, that means the process in which a function calls itself directly or indirectly.
Example of Factorial without recursion

class FactorialExample{
  public static void main(String args[]){
    int i,fact=1;
    int number=5;//It is the number to calculate factorial
   for(i=1;i<=number;i++){
     fact=fact*i;
   }
    System.out.println("Factorial of "+number+" is: "+fact);
   }
}

Example of Factorial with recursion

class FactorialExample2{  
 static int factorial(int n){    
  if (n == 0)    
    return 1;    
  else    
    return(n * factorial(n-1));    
 }    
 public static void main(String args[]){  
  int i,fact=1;  
  int number=4;//It is the number to calculate factorial    
  fact = factorial(number);   
  System.out.println("Factorial of "+number+" is: "+fact);    
 }  
}