How to Read Input from System.in in Java

1. Read Input by Using System.in in Java
2. Read Input Using the System.in and BufferedReader Class in Java
3. Read Input Using the System.console() Method in Java

This tutorial introduces how to read user input from the console using the System.in in Java.

Java provides a low-level stream class System to read user input, which uses an input stream to read input. The System is a class in Java that helps to perform system-related tasks.

We can pass this to the Scanner class, and then by using its methods; we can get user input of several types such as String, int, float, etc. Let’s understand by some examples.

Read Input by Using System.in in Java

Using the System.in in a Java code is easy; pass the class in the Scanner constructor and use the nextLine() method. This method reads and returns a string.

See the example below.

import java.util.Scanner;

public class SimpleTesting {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    System.out.println("Enter a value :");
    String str = sc.nextLine();
    System.out.println("User input: " + str);
  }
}

Output:

Enter a value :
2
User input: 2

Read Input Using the System.in and BufferedReader Class in Java

This is another solution to read user input where we used the BufferedReader class rather than the Scanner class. This code does the same task, and we used the readLine() method here to read the data.

This method belongs to the BufferedReader class and returns a string. See the example below.

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class SimpleTesting {
  public static void main(String[] args) throws IOException {
    System.out.println("Enter a value :");
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    String str = br.readLine();
    System.out.println(str);
  }
}

Output:

Enter a value :
sam
sam

Read Input Using the System.console() Method in Java

Java System class provides a console() method to deal with console-related tasks. So, to read data, we can use this method also.

This method returns a console object by which we can call the readLine() method to read data. See the example below.

import java.io.Console;
import java.io.IOException;

public class SimpleTesting {
  public static void main(String[] args) throws IOException {
    Console c = System.console();
    System.out.println("Enter a value : ");
    String str = c.readLine();
    System.out.println(str);
  }
}

Output:

Enter a value :
sam
sam

The Java Scanner class is commonly used to read user data and provides methods for each data type.

We can use these methods to read specific data. Some of them are below.

public int nextInt(); // reads integer input
public float nextFloat(); // reads decimal input
public String nextLine(); // reads string input

In the example below, we used these methods to read a different type of user input in Java. It will help you to understand the Java console.

See the example below.

import java.io.IOException;
import java.util.Scanner;

public class SimpleTesting {
  public static void main(String[] args) throws IOException {
    Scanner sc = new Scanner(System.in);
    System.out.println("Enter a string value : ");
    String str = sc.nextLine();
    System.out.println(str);
    System.out.println("Enter an int value : ");
    int a = sc.nextInt();
    System.out.println(a);
    System.out.println("Enter a float value : ");
    float f = sc.nextFloat();
    System.out.println(f);
  }
}

Output:

Enter a string value : 
string
string
Enter an int value : 
23
23
Enter a float value : 
34
34.0