Welcome to DrJava.  Working directory is C:\cs12300\from_class
> int[] a1
> a1  = new int[5]
{ 0, 0, 0, 0, 0 }
> int[][] a2
> a2 = new int[2][3]
{ { 0, 0, 0 }, { 0, 0, 0 } }
> int[][][][] a4 = new int[2][2][2][2]
> a4
{ { { { 0, 0 }, { 0, 0 } }, { { 0, 0 }, { 0, 0 } } }, { { { 0, 0 }, { 0, 0 } }, { { 0, 0 }, { 0, 0 } } } }
> a2
{ { 0, 0, 0 }, { 0, 0, 0 } }
> a2[1][1] = 5
5
> a2
{ { 0, 0, 0 }, { 0, 5, 0 } }
> a2[0][2] = 6
6
> a2
{ { 0, 0, 6 }, { 0, 5, 0 } }
> TwoDim.print(a2)
0 0 6 
0 5 0 
> int[][] a20 = new int[20][20]
> a20
{ { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 } }
> TwoDim.print(a20)
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
> TwoDim.print( new int[20][10] )
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
> TwoDim.print( new int[10][10] )
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
> int[][] a10 = new int[10][10]
> TwoDim.print(a10)
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
> TwoDim.diagonal(a10)
{ { 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 }, { 0, 1, 1, 1, 1, 1, 1, 1, 1, 1 }, { 0, 0, 1, 1, 1, 1, 1, 1, 1, 1 }, { 0, 0, 0, 1, 1, 1, 1, 1, 1, 1 }, { 0, 0, 0, 0, 1, 1, 1, 1, 1, 1 }, { 0, 0, 0, 0, 0, 1, 1, 1, 1, 1 }, { 0, 0, 0, 0, 0, 0, 1, 1, 1, 1 }, { 0, 0, 0, 0, 0, 0, 0, 1, 1, 1 }, { 0, 0, 0, 0, 0, 0, 0, 0, 1, 1 }, { 0, 0, 0, 0, 0, 0, 0, 0, 0, 1 } }
> TwoDim.print(a10)
1 1 1 1 1 1 1 1 1 1 
0 1 1 1 1 1 1 1 1 1 
0 0 1 1 1 1 1 1 1 1 
0 0 0 1 1 1 1 1 1 1 
0 0 0 0 1 1 1 1 1 1 
0 0 0 0 0 1 1 1 1 1 
0 0 0 0 0 0 1 1 1 1 
0 0 0 0 0 0 0 1 1 1 
0 0 0 0 0 0 0 0 1 1 
0 0 0 0 0 0 0 0 0 1 
> TwoDim.print( TwoDim.diagonal( new int[12][12] ))
1 1 1 1 1 1 1 1 1 1 1 1 
0 1 1 1 1 1 1 1 1 1 1 1 
0 0 1 1 1 1 1 1 1 1 1 1 
0 0 0 1 1 1 1 1 1 1 1 1 
0 0 0 0 1 1 1 1 1 1 1 1 
0 0 0 0 0 1 1 1 1 1 1 1 
0 0 0 0 0 0 1 1 1 1 1 1 
0 0 0 0 0 0 0 1 1 1 1 1 
0 0 0 0 0 0 0 0 1 1 1 1 
0 0 0 0 0 0 0 0 0 1 1 1 
0 0 0 0 0 0 0 0 0 0 1 1 
0 0 0 0 0 0 0 0 0 0 0 1 
> int[][] weird = new int[3][]
> weird
{ null, null, null }
> weird[0] = new int[4]
{ 0, 0, 0, 0 }
> weird
{ { 0, 0, 0, 0 }, null, null }
> weird[2] = new int[6]
{ 0, 0, 0, 0, 0, 0 }
> weird
{ { 0, 0, 0, 0 }, null, { 0, 0, 0, 0, 0, 0 } }
> weird[1] = weird[2]
{ 0, 0, 0, 0, 0, 0 }
> weird
{ { 0, 0, 0, 0 }, { 0, 0, 0, 0, 0, 0 }, { 0, 0, 0, 0, 0, 0 } }
> weird[1][0] = -3
-3
> weird
{ { 0, 0, 0, 0 }, { -3, 0, 0, 0, 0, 0 }, { -3, 0, 0, 0, 0, 0 } }
> TwoDim.print( weird )
0 0 0 0 
-3 0 0 0 0 0 
-3 0 0 0 0 0 
> int[][] weird = new int[4][]
> weird[0] = new int[6]
{ 0, 0, 0, 0, 0, 0 }
> weird[1] = new int[3]
{ 0, 0, 0 }
> weird[2] = new int[4]
{ 0, 0, 0, 0 }
> weird[3] = new int[2]
{ 0, 0 }
> TwoDim.print( weird )
0 0 0 0 0 0 
0 0 0 
0 0 0 0 
0 0 
>