java - IllegalArgumentException.class as expected in JUnit -

let's have simple method want unit test:

public class add {     public static int addthefollowingpositivenumbertoone(int a) {         if(a <= 0) {             throw new illegalargumentexception();         }         int b = 1 + a;         return b;     } } 

i want make sure illegalargumentexception thrown if parameter less or equal 0.

the junit code this:

@test (expected = illegalargumentexception.class) public void testillegalargumentexception() {     int = -1;     add.addthefollowingpositivenumbertoone(a); } 

why have add .class @ end?

if see api document of expected() parameter, takes parameter of type class. that's why passing illegalargumentexception class type illegalargumentexception.class.