記一次空指針異常

public static void main(String[] args) {
	{
		Object o = null;
		System.out.println(":" + o == null ? "1" : "2");
		//1
	}
	{
		Object o = null;
		System.out.println(":" + (o == null ? "1" : o.toString()));
		//1
	}
	{
			Object o = null;
			System.out.println(":" + o == null ? "1" : o.toString());
			//空指針異常
//			相當於：System.out.println((":" + o) == null ? "1" : o.toString());
	}
}