overriding System.out.format(), doesnt work

[Paul dearrt]

Hi,
how i can override method PrintStream format(format, args)?

I made

 ps = new PrintStream(System.out) {

                @Override
                public void println(String x) {
                    log.append(x + "\n");
                }

                @Override
                public void print(String x) {
                    log.append(x);
                }

                @Override
                public PrintStream format(String format, Object... args) {
                    ps.flush();
                   return super.format(format, args);
                }
            };

and System.setOut(ps);

but method format doesnt work, any idea?

[Paul Clapham]

I would start by finding out what "doesn't work" means. Have a look at our FAQ entry ItDoesntWorkIsUseless for tips on how to do that.

Also, I wrapped your posted code in the "Code" tags for you. See how much easier it is to read now? To do that, just select your code after you paste it into the posting box and click the "Code" button you'll see above the box.

[Paul dearrt]

Paul Clapham wrote:I would start by finding out what "doesn't work" means. Have a look at our FAQ entry ItDoesntWorkIsUseless for tips on how to do that.

Also, I wrapped your posted code in the "Code" tags for you. See how much easier it is to read now? To do that, just select your code after you paste it into the posting box and click the "Code" button you'll see above the box.

Im sorry, I was in hurry.
Doesnt work in this case means: dont formatting text; it only print to PrintStream, without formatting.

[Rob Spoor]

What makes you think that format uses println or print? It's not documented anywhere.

I've checked the source code of PrintStream (just check the src.zip file in your JDK folder), and format treats the PrintStream as an Appender. That means that you would need to override all of the append methods:

@Override
public PrintStream append(char c)
{
    log.append(String.valueOf(c));
    return this;
}

public PrintStream append(CharSequence cs)
{
    String s = (cs == null ? "null" : cs.toString());
    log.append(s);
    return this;
}

public PrintStream append(CharSequence cs, int start, int end)
{
    if (cs == null) cs = "null";
    log.append(cs.subSequence(start, end).toString());
    return this;
}

That still doesn't mean all methods work. You need to override all of the other print and println methods as well, as these each call a private method called write (and the println methods also a private method called newLine()) which you cannot override. In other words, you'll probably have to override every single method...