Java System setErr() Method

Description

The Java System setErr() method reassigns the "standard" error output stream.

Declaration

Following is the declaration for java.lang.System.setErr() method

public static void setErr(PrintStream err)

Parameters

err − This is the new standard error output stream.

Return Value

This method does not return any value.

Exception

SecurityException − if a security manager exists and its checkPermission method doesn't allow reassigning of the standard error output stream.

Example: Setting Error Stream as File

The following example shows the usage of Java System setErr() method. In this program, we've created a FileOutputStream object and initialized it with underlying file.txt. Then using setErr() method, we've set the error output to the file and then message is printed.

package com.tutorialspoint;

import java.io.FileOutputStream;
import java.io.PrintStream;

public class SystemDemo {

   public static void main(String[] args) throws Exception {

      // create a file
      FileOutputStream f = new FileOutputStream("file.txt");
 
      System.setErr(new PrintStream(f));
      
      // redirect the output
      System.err.println("This will get redirected to file");
   }
} 

Output

Let us assume we have a text file file.txt which gets generated as an output for our example program.The file content consist of −

This will get redirected to file

Example: Setting Error Stream as Console

The following example shows the usage of Java System setErr() method. In this program, using setErr() method, we've set the error output to the console and then message is printed.

package com.tutorialspoint;

public class SystemDemo {

   public static void main(String[] args) throws Exception {
 
      System.setErr(System.out);
      
      // redirect the output
      System.err.println("This will get redirected to console");
   }
} 

Output

Let us compile and run the above program, this will produce the following result −

This will get redirected to console