java - 初始化包装对象

Question

这个问题已经有答案了:

what is difference between integer a = 5 and new Integer(5)? (5 个回答)

已关闭 8 年前。

怎么样Integer x1 = 5;不同于Integer x1 = new Integer(5);

Integer x1 = 5; // created through boxing
Integer x2 = 5;
Integer x3 = new Integer(5); // no boxing
Integer x4 = new Integer(5);
if (x1 == x2) System.out.println("Same object"); //prints
if (x3 == x4) System.out.println("Same object"); //doesn't print

正如我所预期的那样，此代码不会显示相同的对象两次。为什么？

PS:规则是:为了节省内存，以下包装对象的两个实例当它们的原始值相同时总是==:Boolean；字节;字符从\u 到\u007f；从 -128 到 127 的短整型

Answer 1

// Prints because of autoboxing ie it converts to integer value.
if (x1 == x2) System.out.println("Same object"); 
/* 
 * Doesn't prints because of creating an object(x3) using Integer wrapper class 
 * which is different from other object x4. ie both are different object 
 * pointing to different memory location in memory.
 */
if (x3 == x4) System.out.println("Same object");