Console readLine() method in Java with Examples

The readLine() method of Console class in Java is of two types:

1. The readLine() method of Console class in Java is used to read a single line of text from the console.

Syntax:

public String readLine()

Parameters: This method does not accept any parameter.

Return value: This method returns the string containing the line that is read from the console. It returns null if the stream has ended.



Exceptions: This method throws IOError if an I/O error occurs.

Note: System.console() returns null in an online IDE.

Below programs illustrate readLine() method in Console class in IO package:

Program 1:

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// Java program to illustrate
// Console readLine() method
  
import java.io.*;
  
public class GFG {
    public static void main(String[] args)
    {
        // Create the console object
        Console cnsl
            = System.console();
  
        if (cnsl == null) {
            System.out.println(
                "No console available");
            return;
        }
  
        // Read line
        String str = cnsl.readLine(
            "Enter string : ");
  
        // Print
        System.out.println(
            "You entered : " + str);
    }
}

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Output:

Program 2:

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// Java program to illustrate
// Console readLine() method
  
import java.io.*;
  
public class GFG {
    public static void main(String[] args)
    {
        // Create the console object
        Console cnsl
            = System.console();
  
        if (cnsl == null) {
            System.out.println(
                "No console available");
            return;
        }
  
        // Read line
        String str = cnsl.readLine(
            "Enter string : ");
  
        // Print
        System.out.println(
            "You entered : " + str);
    }
}

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Output:

2. The readLine(String, Object) method of Console class in Java is used to read a single line of text from the console by providing a formatted prompt.

Syntax:

public String readLine(String fmt,
                      Object... args)

Parameters: This method accepts two parameters:



  • fmt – It represents the format of the string.
  • args – It represents the arguments that are referenced by the format specifiers in the string format.

Return value: This method returns the string that contains the line read from the console. It returns null if the stream is ended.

Exceptions:

  • IllegalFormatException – This method throws IllegalFormatException if string format contains an illegal syntax or a format specifier is not compatible with the given arguments or insufficient arguments given the format string or other conditions that are illegal.
  • IOError – This method throws IOError if an I/O error occurs.

Below programs illustrate readLine(String, Object) method in Console class in IO package:

Program 1:

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// Java program to illustrate
// Console readLine(String, Object) method
  
import java.io.*;
  
public class GFG {
    public static void main(String[] args)
    {
        // Create the console object
        Console cnsl
            = System.console();
  
        if (cnsl == null) {
            System.out.println(
                "No console available");
            return;
        }
  
        String fmt = "%1$4s %2$10s %3$10s%n";
  
        // Read line
        String str
            = cnsl.readLine(
                fmt, "Enter", "string : ");
  
        // Print line
        System.out.println(
            "You entered : " + str);
    }
}

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Output:

Program 2:

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// Java program to illustrate
// Console readLine(String, Object) method
  
import java.io.*;
  
public class GFG {
    public static void main(String[] args)
    {
        // Create the console object
        Console cnsl
            = System.console();
  
        if (cnsl == null) {
            System.out.println(
                "No console available");
            return;
        }
  
        String fmt = "%1$4s %2$10s %3$10s%n";
  
        // Read line
        String str
            = cnsl.readLine(
                fmt, "Enter", "string : ");
  
        // Print line
        System.out.println(
            "You entered : " + str);
    }
}

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Output:

References:
1. https://docs.oracle.com/javase/10/docs/api/java/io/Console.html#readLine()
2. https://docs.oracle.com/javase/10/docs/api/java/io/Console.html#readLine(java.lang.String, java.lang.Object…)

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