can i write a similar class as "System" for printing something?

Question

can i build a user-defined class for printing anything using printstream variable just as "System" class ?

so what i did is:

    import java.io.*;

    public final class SystemDemo{



public final static InputStream give=null;//the same variables 

public final static PrintStream take=null;

public final static PrintStream error = null;

}

and wanted to use this SystemDemo class as "System"(pre-defined) ,like

    SystemDemo.take.println("something");

but i get a NullPointerException .

You are setting variables as `null`, *and* you're getting NPE? That's *almost* impossible. ;) Just kidding... — zlakad, Feb 10 '18 at 08:15
The System class declaration uses some clever magic to initialize the `in` and `out` and `err` streams. You don't want to do that. (Not least because it probably won't work reliably. The `System` class gets special support from the JIT compiler to make it work properly.) — Stephen C, Feb 10 '18 at 08:20

score 0 · Accepted Answer · answered Feb 10 '18 at 08:28

0

You can try this, will work same for your requirement,

 public final class SystemDemo
 {
    public final static PrintStream take =  new PrintStream(System.out);
 }

And then use this as,

SystemDemo.take.println("Your String");

It worked fine, tested with Netbeans.

answered Feb 10 '18 at 08:28

Mrunmay Deswandikar

108
1
7

thanks @mrunmay-deswandikar – nikhil2000 Feb 10 '18 at 08:37
Yea. This is the part that you can do safely. The part that you can't do is emulate the behavior of `System.setIn()` etcetera and the "magic" that `System` uses to *actually* initialize the `final` variables. Using nasty reflection or `Unsafe` is not guaranteed to work reliably for modifying `final` variables. – Stephen C Feb 11 '18 at 02:03
Right, the main part is we can't get from API, how the out object is internally initialized, if we try to initialize, any custom Out object, we can't manage it. Java internally handles this. – Mrunmay Deswandikar Feb 19 '18 at 12:16

can i write a similar class as "System" for printing something?

1 Answers1