Console readLine() method in Java with Examples (original) (raw)
Last Updated : 12 Jun, 2020
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:
import java.io.*;
public class GFG {
`` public static void main(String[] args)
`` {
`` Console cnsl
`` = System.console();
`` if (cnsl == null ) {
`` System.out.println(
`` "No console available" );
`` return ;
`` }
`` String str = cnsl.readLine(
`` "Enter string : " );
`` System.out.println(
`` "You entered : " + str);
`` }
}
Output:
Program 2:
import java.io.*;
public class GFG {
`` public static void main(String[] args)
`` {
`` Console cnsl
`` = System.console();
`` if (cnsl == null ) {
`` System.out.println(
`` "No console available" );
`` return ;
`` }
`` String str = cnsl.readLine(
`` "Enter string : " );
`` System.out.println(
`` "You entered : " + str);
`` }
}
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:
import java.io.*;
public class GFG {
`` public static void main(String[] args)
`` {
`` Console cnsl
`` = System.console();
`` if (cnsl == null ) {
`` System.out.println(
`` "No console available" );
`` return ;
`` }
`` String fmt = "%1$4s %2$10s %3$10s%n" ;
`` String str
`` = cnsl.readLine(
`` fmt, "Enter" , "string : " );
`` System.out.println(
`` "You entered : " + str);
`` }
}
Output:
Program 2:
import java.io.*;
public class GFG {
`` public static void main(String[] args)
`` {
`` Console cnsl
`` = System.console();
`` if (cnsl == null ) {
`` System.out.println(
`` "No console available" );
`` return ;
`` }
`` String fmt = "%1$4s %2$10s %3$10s%n" ;
`` String str
`` = cnsl.readLine(
`` fmt, "Enter" , "string : " );
`` System.out.println(
`` "You entered : " + str);
`` }
}
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…)