Explain me this code's working please

Question

https://code.sololearn.com/cd2m6X2qZPnF/?ref=app
Also what if we replace printf with print why does it give error

Answer 1

more detailed,
java.io.PrintStream.printf() and java.io.PrintStream.append() return PrintStream object so you can test if it is null. Printstream send chars from printf() and append() methods to output, ( to screen ).
It is possible use printf() with only one parameter because other parameters are in Object... args, which can be empty.

print return void so you cant test if it is null, because void is not object, it is keyword which means "no value is return".

class java.io.PrintStream
PrintStream printf​(String format, Object... args)
PrintStream append​(CharSequence csq)
void print​(String s)

Answer 2

check how it returns object PrintStream

import java.io.PrintStream;
...
var s = new PrintStream(System.out);
Object ps = s.printf("some text\n"); // some text
System.out.println(ps == s); // true

Answer 3

zemiak bro you r too techinical I have not very advance in java but yeah I am getting somethig .It would be a great of u if u explain properlu