SRK SRK - 7 months ago 38
Java Question

Redirect console output to string in java

I have one function whose return type is VOID and it prints directly on console.

However I need that output in string so that I can work on it.

As I cant make any changes with function with return type is VOID so I have to redirect that output to string.

How can I redirect it in JAVA?

There are many questions regarding redirecting stdout to string but they redirect only input taken from user and not output of some function...

Answer

If the function is printing to System.out, you can capture that output by using the System.setOut method to change System.out to go to a PrintStream provided by you. If you create a PrintStream connected to a ByteArrayOutputStream, then you can capture the output as a String.

Example:

    // Create a stream to hold the output
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    PrintStream ps = new PrintStream(baos);
    // IMPORTANT: Save the old System.out!
    PrintStream old = System.out;
    // Tell Java to use your special stream
    System.setOut(ps);
    // Print some output: goes to your special stream
    System.out.println("Foofoofoo!");
    // Put things back
    System.out.flush();
    System.setOut(old);
    // Show what happened
    System.out.println("Here: " + baos.toString());

This program prints just one line:

    Here: Foofoofoo!
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