What the various types of assert methods and it purpose?

Answer 1

Suppose you assume that a number passed into a method (say, methodOne()) will never be negative. While testing and debugging, you want to validate your assumption, but you don't want to have to strip out print statements, runtime exception handlers, or if/else tests when you're done with development. But leaving any of those in is, at the least, a performance hit. Assertions to the rescue!

Assertions work quite simply. You always assert that something is true. If it is, no problem. Code keeps running. But if your assertion turns out to be wrong (false), then a AssertionError is thrown right then and there, so you can fix whatever logic flaw led to the problem. Assertions come in two flavors: really simple and simple, as follows: Really simple: private void doSomething() { assert (y > x); // more code assuming y is greater than x } Simple: private void doSomething() { assert (y > x): "y is " + y + " x is " + x; // more code assuming y is greater than x }