added

Java test cases still have wrong syntax.

Use

  assertEquals("undefined",s.slope(new int[] {-7,2,-7,4}));
  assertEquals("5",s.slope(new int[] {10,50,30,150}));
  assertEquals("-5",s.slope(new int[] {15,45,12,60}));
  assertEquals("6",s.slope(new int[] {10,20,20,80}));
  assertEquals("undefined",s.slope(new int[] {-10,6,-10,3}));

these issues were fixed a long time ago.
Apologies for the late reply

Fixed about a week ago.

it was static instead of class before

Fixed :)