How Java takes the file name and line number from the source file

How to take the file name and line number in the Java source code file:

In the C + + program, the compiler provides two macros to support the acquisition of line numbers and file names in the source file, the two macros are __file__,__line__

You can print line numbers and file names in the following ways

1.#include　<stdio.h>
2.int　main()
3.{
4.　fprintf(stdout,"[%s:%d]　Hello　World!",__FILE__,__LINE__);
5.　return　0;
6.}

But without these two macros in Java, how do we get the filename and line number, and flip through the JDK, we find the Stacktraceelement class. This class can be obtained from the throwable and can also be obtained from the thread class, through which I write the following test procedure for a print line number:

01.public　class　LineNo　{
02.　public　static　int　getLineNumber()　{
03.　return　Thread.currentThread().getStackTrace()[2].getLineNumber();
04.　}
05.　
06.　public　static　String　getFileName()　{
07.　return　Thread.currentThread().getStackTrace()[2].getFileName();
08.　}
09.　public　static　void　main(String　args[])　{
10.　System.out.println("["+getFileName()+"："+　getLineNumber()+"]"+"Hello　World!");
11.　}
12.}

Leaving a question, what does the magic number 2 in the above program mean?