Java - Getting Input From User

In java language, we can take the values from the user instead of assigning at the time of compilation.

Why does values are required from user?

• Consider a situation when we want to perform addition of two numbers. If we assign values as int a = 10, b = 20; then while running the program we will not change any values.
• We will get always result as 30 from above two numbers.
• We always need to go back to the code and assign the different values to see the different result.

How to get values from user?

Java allows us to get values from user throw the keyboard input by using following 3 ways.

1. By Commandline Argument
2. By Scanner class
3. By BufferedReader class

1. By Commandline Argument

Commandline argument is one of the esiest way to take values from user while runnign the program.

Note : We have already studies about the commandline argument.

Learn commandline argument

2. By Scanner Class

Second way of getting input from user is by using the scanner class.

Steps for use

1. import package - java.util.Scanner;
2. Create scanner class object to use their methods.
3. Call the specific method using scanner class object.

Example

Accepting integer from user and displaying using scanner.

import java.util.Scanner;  
class ScannerTest
{  
   public static void main(String args[])
   {  
      Scanner sc = new Scanner(System.in);  
      int value;
      System.out.println("Enter any number : ");  
      value = sc.nextInt();  
        
      System.out.println("You have entered : "+value);  
   }
} 

Output

How to get other type values?

Java provides several different methods to get different type values as.

3. By BufferedReader class

BufferedReader is mostly used in the file handling concept. BufferedReader have fast performance while taking input from user.

Note: BufferedReader need to type into other type before use.

How to use BufferedReader class

1. import package - java.io.*;
2. Create object of InputStreamReader class by passing System.in
3. Create object of BufferedReader class and pass InputStreamReader object in it's constructor.
4. Call method by using BufferedReader object.

Example

The method readLine() method generates an exception hence it is written inside the try-catch block.

import java.io.*;
class ScannerTest
{  
   public static void main(String args[])
   {  
      InputStreamReader isr = new InputStreamReader(System.in);
      BufferedReader br = new BufferedReader(isr);  
      String value = null;
        
      try 
      {
	 value = br.readLine();
      }  
      catch (IOException e) 
      {
	 // TODO Auto-generated catch block
	 e.printStackTrace();
      }
        
      System.out.println("You have entered : "+value);  
   }
}

Output