Arrays.sort(Object[] a) - how is it implemented?

Question

Are there any resources on how the mergeSort used by Arrays.sort(Object[] a) is implemented? While it is documented quite good, I have a hard time understanding it (especially why the src and dest are are switched when mergeSort() get's recursively called).

Solution

Here is the source of java.util.Arrays.

Actually, you have that source code in the JDK - just open java.util.Arrays in your IDE and the source code + the comments will appear. If you don't have an IDE, look at JDK_HOME\src.zip

Then, put it in your IDE and trace how it works.

• put breakpoints (and run a program in debug mode)
• use System.out.println(..)
• change parts of it to see how they are reflected.
• read the wikipedia article about merge sort
• pay attention to this comment: // Recursively sort halves of dest into src