How to clear the console?

Question

Since there are several answers here showing non-working code for Windows, here is a clarification:

Runtime.getRuntime().exec("cls");

This command does not work, for two reasons:

1. There is no executable named cls.exe or cls.com in a standard Windows installation that could be invoked via Runtime.exec, as the well-known command cls is builtin to Windows’ command line interpreter.

2. When launching a new process via Runtime.exec, the standard output gets redirected to a pipe which the initiating Java process can read. But when the output of the cls command gets redirected, it doesn’t clear the console.

To solve this problem, we have to invoke the command line interpreter (cmd) and tell it to execute a command (/c cls) which allows invoking builtin commands. Further we have to directly connect its output channel to the Java process’ output channel, which works starting with Java 7, using inheritIO():

import java.io.IOException;

public class CLS {
    public static void main(String... arg) throws IOException, InterruptedException {
        new ProcessBuilder("cmd", "/c", "cls").inheritIO().start().waitFor();
    }
}

Now when the Java process is connected to a console, i.e. has been started from a command line without output redirection, it will clear the console.

You can use following code to clear command line console:

public static void clearScreen() {  
    System.out.print("\033[H\033[2J");  
    System.out.flush();  
}  

For further references visit: http://techno-terminal.blogspot.in/2014/12/clear-command-line-console-and-bold.html

This is how I would handle it. This method will work for the Windows OS case and the Linux/Unix OS case (which means it also works for Mac OS X).

public final static void clearConsole()
{
    try
    {
        final String os = System.getProperty("os.name");

        if (os.contains("Windows"))
        {
            Runtime.getRuntime().exec("cls");
        }
        else
        {
            Runtime.getRuntime().exec("clear");
        }
    }
    catch (final Exception e)
    {
        //  Handle any exceptions.
    }
}

Note that this method generally will not clear the console if you are running inside an IDE.

Create a method in your class like this: [as @Holger said here.]

public static void clrscr(){
    //Clears Screen in java
    try {
        if (System.getProperty("os.name").contains("Windows"))
            new ProcessBuilder("cmd", "/c", "cls").inheritIO().start().waitFor();
        else
            Runtime.getRuntime().exec("clear");
    } catch (IOException | InterruptedException ex) {}
}

This works for windows at least, I have not checked for Linux so far. If anyone checks it for Linux please let me know if it works (or not).

As an alternate method is to write this code in clrscr():

for(int i = 0; i < 80*300; i++) // Default Height of cmd is 300 and Default width is 80
    System.out.print("\b"); // Prints a backspace

I will not recommend you to use this method.

A way to get this can be print multiple end of lines ("\n") and simulate the clear screen. At the end clear, at most in the unix shell, not removes the previous content, only moves it up and if you make scroll down can see the previous content.

Here is a sample code:

for (int i = 0; i < 50; ++i) System.out.println();

If you want a more system independent way of doing this, you can use the JLine library and ConsoleReader.clearScreen(). Prudent checking of whether JLine and ANSI is supported in the current environment is probably worth doing too.

Something like the following code worked for me:

import jline.console.ConsoleReader;

public class JLineTest
{
    public static void main(String... args)
    throws Exception
    {
        ConsoleReader r = new ConsoleReader();

        while (true)
        {
            r.println("Good morning");
            r.flush();

            String input = r.readLine("prompt>");

            if ("clear".equals(input))
                r.clearScreen();
            else if ("exit".equals(input))
                return;
            else
                System.out.println("You typed '" + input + "'.");

        }
    }
}

When running this, if you type 'clear' at the prompt it will clear the screen. Make sure you run it from a proper terminal/console and not in Eclipse.

Try the following :

System.out.print("\033\143");

This will work fine in Linux environment