User and Programmer Interface:

Use Scanner class to take keyboard information.

Examples:

import java.util.Scanner;

public class UserInterface
{
   public static void main(String[] args)
   {
     Scanner sc = new Scanner(System.in);
     System.out.println("Enter two numbers");
     int num1 = sc.nextInt(); //public int nextInt()
     int num2 = sc.nextInt(); //Scans the next token of the input as an int.
     System.out.println('\n'+"You entered "+num1+ " and "+num2+"."+'\n');
     System.out.println(num1 + " + " +num2 + " = " +(num1+num2));
   }
}

import java.util.Scanner;

public class UserInterface
{
   public static void main(String[] args)
   {
     Scanner sc = new Scanner(System.in);
     System.out.println("Enter your first name");
     String name = sc.next();
     System.out.println('\n'+"Your name is "+name+".");
   }
}

import java.util.Scanner;

public class UserInterface
{
   public static void main(String[] args)
   {
     Scanner sc = new Scanner(System.in);
     System.out.println("Enter the unit price:");
     double price = sc.nextDouble();
     System.out.println('\n'+"The unit price is "+price+".");
   }
}

import java.util.Scanner;

public class UserInterface
{
   public static void main(String[] args)
   {
     Scanner sc = new Scanner(System.in);
     System.out.println("Enter your name");
     String name = sc.nextLine();
     System.out.println('\n'+"Your name is "+name+".");
   }
}

Using Dialog Boxes for Input and Output

import javax.swing.JOptionPane;

public class UserInterface
{
   public static void main(String[] args)
   {
 	String input = JOptionPane.showInputDialog("Enter price:");
 	double price = Double.parseDouble(input);
 	JOptionPane.showMessageDialog(null, "Price: " + price);
 	System.exit(0);
   }
}

import javax.swing.JOptionPane;

public class UserInterface
{
   public static void main(String[] args)
   {
 	String input = JOptionPane.showInputDialog("Enter the first integer:");
 	int num1 = Integer.parseInt(input);
 	String input1 = JOptionPane.showInputDialog("Enter the second integer:");
 	int num2 = Integer.parseInt(input1); 	
 	JOptionPane.showMessageDialog(null, num1 + " + " + num2 + " = " + (num1+num2));
 	System.exit(0);
   }
}

import javax.swing.JOptionPane;

public class UserInterface
{
   public static void main(String[] args)
   {
 	String input = JOptionPane.showInputDialog("Enter your name:");
 	JOptionPane.showMessageDialog(null, "Nice to meet you, " + input);
 	System.exit(0);
   }
}