Java - How to use PrintStream/OutputStream to print to the Command Line

Question

I know we can use PrintStream to print lines to a given file:

    PrintStream output;
    output = new PrintStream("./temp.txt");
    output .println("some output text"); 

However, can we use PrintStream to print lines to the command line?

I've looked through the Java docs and it seems PrintStream constructor can take a file path or an OutputStream (is there a OutputStream subclass that would print to command line?)

Solution 1

output = new PrintStream(System.out);

or actually,

output = System.out;

Similarly, you can do the same with System.err ... So why don't we just simply use System.out and System.err directly? sout + tab is quite fast to type in IntelliJ

Solution 2

System.out or System.error are already PrintStream and we can use them to print the output to command line without creating a new PrintStream object that you are doing.

Advantage of using this printStream is that you can use System.setOut() or System.setErr() to set the printSteam of your choice

PrintStream output = new PrintStream("./temp.txt");
System.setOut(output); 

Above will override the default Printstream of printing to command line and now calling System.out.println() will print everything in given file(temp.txt)

Comments

[L.Spillner]

Sidenote: By definition System.out (stdout / Standard Outputstream) already is a PrintStream.

[Per Lundberg]

Note that using System.setOut() and System.setErr() replaces the standard output or standard error stream for the whole process. For a small, minimal console application this might be fine. For larger systems, complex unit/integration tests, etc., this can have severe consequences (if e.g. different parts of the system modifies these streams from multiple threads simultaneously).