static method

Best way to develop and maintain a large program is to construct it from small, simple pieces, or modules.

import java.util.Scanner;

public class Choice 
{
   public static void main( String[] args )
   {
    	int selection = 0;
	
    	Scanner input = new Scanner(System.in);

    	menu();  // call a static method without an object.
    	selection = input.nextInt();
        System.out.printf("Your choice is %d\n", selection);
   } 
	 
   public static void menu()
   {
     System.out.println("Which of the following would you like to do?"); 
     System.out.println("\t1. Do addition."); 
     System.out.println("\t2. Do subtraction."); 
     System.out.println("\t3. Do multiplication."); 
     System.out.println("\t4. Do division."); 
     System.out.println("\t5. quit"); 
     System.out.print("Enter your selection ( 1 to 5 ):   ");
   }
}

import java.util.Scanner;

public class Choice 
{
   public static void main( String[] args )
   {
    	int selection = 0;
	
    	Scanner input = new Scanner(System.in);

      while(selection != 5)
      {
    	   menu();  // call a static method without an object.
    	   selection = input.nextInt();
           System.out.printf("Your choice is %d\n", selection);
      }
   } 
	 
   public static void menu()
   {
     System.out.println("Which of the following would you like to do?"); 
     System.out.println("\t1. Do addition."); 
     System.out.println("\t2. Do subtraction."); 
     System.out.println("\t3. Do multiplication."); 
     System.out.println("\t4. Do division."); 
     System.out.println("\t5. quit"); 
     System.out.print("Enter your selection ( 1 to 5 ):   ");
   }
}

import java.util.Scanner;

public class Choice 
{
   public static void main( String[] args )
   {
    	int selection = 0;
	
    	Scanner input = new Scanner(System.in);

      while(selection != 5)
      {
    	   menu();  // call a static method without an object.
    	   selection = input.nextInt();
         System.out.printf("Your choice is %d\n", selection);
         echo(selection);
      }
   } 
	 
   public static void menu()
   {
     System.out.println("Which of the following would you like to do?"); 
     System.out.println("\t1. Do addition."); 
     System.out.println("\t2. Do subtraction."); 
     System.out.println("\t3. Do multiplication."); 
     System.out.println("\t4. Do division."); 
     System.out.println("\t5. quit"); 
     System.out.print("Enter your selection ( 1 to 5 ):   ");
   }

   public static void echo(int i)
   {
     switch(i)
     {
       case 1:  System.out.println("You would like to do addition.");
                break; 
       case 2:  System.out.println("You would like to do subtraction.");
                break; 
       case 3:  System.out.println("You would like to do multiplication.");
                break; 
       case 4:  System.out.println("You would like to do division.");
                break; 
       case 5:  System.out.println("Good Bye!");
                break; 
       default:  System.out.println("Please select 1 to 5."); 
     }    
   }
}

import java.util.Scanner;

public class Choice 
{
   public static void main( String[] args )
   {
    	int selection = 0;
	
    	Scanner input = new Scanner(System.in);

      while(selection != 5)
      {
    	   menu();  // call a static method without an object.
    	   selection = input.nextInt();
         System.out.printf("Your choice is %d\n", selection);
         echo(selection);
      }
   } 
	 
   public static void menu()
   {
     System.out.println("Which of the following would you like to do?"); 
     System.out.println("\t1. Do addition."); 
     System.out.println("\t2. Do subtraction."); 
     System.out.println("\t3. Do multiplication."); 
     System.out.println("\t4. Do division."); 
     System.out.println("\t5. quit"); 
     System.out.print("Enter your selection ( 1 to 5 ):   ");
   }

   public static void echo(int i)
   {
     if (i == 5)
        System.out.println("Good Bye!");
     else
     {
          if(i < 5)
          {
               Couple obj = new Couple();

               switch(i)
               {
          	case 1:  obj.add();
                	   break; 
          	case 2:  obj.subtract();
                	   break; 
          	case 3:  obj.multiply();
                	   break; 
          	case 4:  obj.divide();
                	   break;
        	}
           }
           else 
           	 System.out.println("Please select 1 to 5.");
      }    
   }
}

Create a class named Couple with two instance int variables, a, b. The constructor will take nothing from caller, but take two numbers from user. There are four methods, add(), subtract(), multiply(), and divide(). They will perform the tasks as following:

For example,
If users input 4 and 2,
(1) the add method will print
        4 + 2 = 6
(2) the subtract method will print
        4 - 2 = 2
(3) the multiply method will print
        4 * 2 = 8
(4) the divide method will print
        4 / 2 = 2
If users input 4 and 0,
the divide method will print
You can not divide them since divisor is zero.

//There is another version for declaring an object in each case.

   public static void echo(int i)
   {
     if (i == 5)
        System.out.println("Good Bye!");

     else
     {     
       switch(i)
        {
          case 1:  Couple obj = new Couple(); 
                   obj.add();
                   break; 
          case 2:  Couple obj1 = new Couple(); 
                   obj1.subtract();
                   break; 
          case 3:  Couple obj2 = new Couple(); 
                   obj2.multiply();
                   break; 
          case 4:  Couple obj3 = new Couple(); 
                   obj3.divide();
                   break; 
          default:  System.out.println("Please select 1 to 5.");
        }
     }    
   }