Product Version = NetBeans IDE 8.1 (Build 201510222201)
Operating System = Windows 10 version 10.0 running on amd64
Java; VM; Vendor = 1.8.0_72
Runtime = Java HotSpot(TM) 64-Bit Server VM 25.72-b15

Reproducibility: Happens every time

STEPS:
  * Open dialog Foo
  * Click on button "Click me"

ACTUAL:
  nothing happens

EXPECTED:
  message pops up

Assume an enumeration

public enumeration testEnum{
	ONE,
	TWO,
	THREE;
}

Assume a method in some class

public String toString(testEnum t) {
	String s;
	if (t == testEnum.ONE) {
		s = "1";
	} else if (t == testEnum.TWO) {
		s = "2";
	} else {
		s = "3";
	}
	return "number is " + s;
}

On the first if statement a hint is given "replace chain of ifs with switch".
Applying this hint will give:

public String toString(testEnum t) {
	String s;
	if (null != t) switch (t) {
		case ONE:
			s = "1";
		case TWO:
			s = "2";
		default:
			s = "3";
	}
	return "number is " + s;
}

First of all now suddenly an error appears in the code because s might not have been initialized. Apart from that, why is there a need for the additional null != t check, because whenever in the initial code
t would be null on entry of the toString function the default switch case/label would have been applied or am I wrong?