Log.java Productive Java logging measure the time in ms between two calls to System.out.println This allow simple java code to be benchmarked.

Log.java

/*
Productive Java logging
measure the time in ms
between two calls to System.out.println
This allow simple java code to be benchmarked.

Have a great day!
- Xerxes Rånby
2021 12 14

$ java Log.java
[        0] Hello World
[       12] Hello World
*/
import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintStream;

public class Log extends OutputStream {
  
    public static void main(String[] args) {
        System.setOut(new PrintStream(new Log()));
        System.out.println("Hello World");
        System.out.println("Hello World");
    }

    private final long t0 = System.currentTimeMillis();
    private volatile long oldTime;
    private final PrintStream err;

    private Log() {
        this.err = System.err;
        oldTime = System.currentTimeMillis();
    }

    @Override
    public void write(byte[] b) {
        err.print(b);
    }
    
    @Override
    public void write(byte[] b, int off, int len) {
        String s = new String(b).substring(off, len);
        if(s.equals("\n")){
            err.print(s);
            return;
        }
        print(s);
    }
    
    @Override
    public void write(int i) throws IOException {
        err.write(i);
    }

    public void print(final String message) {
        err.printf("[%,9d] %s", getStartupDiff(), message);
    }

    public long getStartupDiff() {
        final long time = System.currentTimeMillis();
        oldTime = time;
        return time - t0;
    }
}