基本上它将被编译为：

Integer i = Integer.valueOf(NumberUtils.INTEGER_ONE);

假定 INTEGER_ONE 被声明为 int 。

在执行时，假设INTEGER_ONE的值为1，则实际上将返回对的引用每次相同的对象，由Java语言规范保证，因为它的范围是-128到127。超出该范围的值可以返回对同一对象的引用，但是没有

At execution time, assuming INTEGER_ONE has the value 1, that will actually return a reference to the same object each time, guaranteed by the Java Language Specification, because it's in the range -128 to 127. Values outside that range can return references to the same object, but don't have to.