java Integer自动拆箱引发的NPE以及常量池导致的判等问题[-128 127]为常量池
Integer a1 = 250; Integer a2 = 250; Integer b1 = 25; Integer b2 = 25; Integer b3 =null; int b4 = 5; System.out.println(a1 == a2);//false System.out.println(b1 == b2);//true System