Write it, run it, read the output

This is a scratch drill — your code runs, nothing is graded or recorded. No test cases, no expected output, no verdict.

TASK

Write the Java program so it prints the upper-triangle output and then the lower-triangle output of the fixed 4 x 4 matrix. Preserve four entries per row and print 0 at every excluded position.

4 2 7 1
0 5 3 8
0 0 11 12
0 0 0 16

4 0 0 0
9 5 0 0
6 10 11 0
13 14 15 16