driver function
public static void main ( String argc [ ] ) { int [ ] [ ] mat = { { 1 , 3 , 5 , 3 } , { 0 , 4 , 6 , 2 } , { 0 , 0 , 2 , 5 } , { 0 , 0 , 0 , 6 } } ; if ( isUpperTriangularMatrix ( mat ) ) System . out . println ( " Yes " ) ; else System . out . println ( " No " ) ; } }