为什么它给出了真实我的意思是我将有一些其他的内存位置和i2有不同它必须给出错误 [英] Why its giving true I mean I will have some other memory location and i2 have different it must give false

问题描述

为什么它给出真实我的意思是我会有一些其他的内存位置和i2有不同它必须给出错误？



i写了这段代码为什么它给出了真实我应该知道什么原因。有人知道答案然后tellllllllllllllllllllllllllllllllllllllllll我

why its giving true i mean i will have some other memory location and i2 have different it must give false ??

i have written this code why its give true and i what to know reason.can somebody know the answer then tellllllllllllllllllllllllllllllllllllllll me

public class ADS {
  public static void main(String[] args) {
    int i=new Integer(10);
    int i2=10;
    System.out.println(i==i2);
  }
}

我的尝试：



嘿任何人都说明为什么它给出了真实我的意思是我会有一些其他的记忆位置和i2有不同它必须给出错误？

What I have tried:

hey anyone give reason why its giving true i mean i will have some other memory location and i2 have different it must give false ??

推荐答案

这些是整数值，而不是整数值的指针。

因此，比较运算符进行值比较;因为两个值都相等，所以它返回true。

These are integer values, not pointers to integer values.
Thus, the comparison operator does a value comparison; since both values are equal, it returns true.

如果你这样做：

Integer i = new Integer(10);
Integer i2 = new Integer(10);
System.out.println(i==i2);

然后你可能获得 false 。



如果你这样做：

then you'll probably get false.

If you do:

Integer i = Integer.valueOf(10);
Integer i2 = 10;
System.out.println(i==i2);

然后你会得到 true ，因为<$ c $之间的值c> -128 和 127 会自动缓存：

Java陷阱 - OWASP [ ^ ]

章节  5. 转化和促销 [ ^ ]



如果您申报变量为 int 而不是 Integer ，那么你将获得 true 因为你正在执行一个值相等测试，而不是一个参考相等测试。

then you'll get true, because values between -128 and 127 are automatically cached:
Java gotchas - OWASP[^]
Chapter 5. Conversions and Promotions[^]

If you declare the variables as int rather than Integer, then you'll get true because you're performing a value equality test, not a reference equality test.

你必须明白那两行s是两种说同样的方法。

You have to understand that those 2 lines are 2 ways to say the same thing.

int i=new Integer(10);
int i2=10;

这两行是10的整数，所以它们是相等的。

使用调试器并自己看看。



有一个工具可以让你看到你的代码在做什么，它的名字是调试器。它也是一个很好的学习工具，因为它向你展示了现实，你可以看到哪种期望与现实相符。

当你不明白你的代码在做什么或为什么它做它做的时候，答案就是答案是调试器。

使用调试器查看代码正在执行的操作。只需设置断点并查看代码执行情况，调试器允许您逐行执行第1行并在执行时检查变量。



调试器 - 维基百科，免费的百科全书 [ ^ ]



掌握Visual Studio 2010中的调试 - 初学者指南 [ ^ ]

使用Visual Studio 2010进行基本调试 - YouTube [ ^ ]

HTTP：//docs.or acle.com/javase/7/docs/technotes/tools/windows/jdb.html [ ^ ]

https://www.jetbrains.com/idea/help/debugging-your-first-java-application.html [ ^ ]

调试器在这里向您展示您的代码正在做什么，您的任务是与它应该做什么进行比较。

调试器中没有魔法，它没有发现错误，它只是帮助你到。当代码没有达到预期的效果时，你就会接近一个错误。

The 2 lines are integers of value 10, so they are equal.
Use the debugger and see by yourself.

There is a tool that allow you to see what your code is doing, its name is debugger. It is also a great learning tool because it show you reality and you can see which expectation match reality.
When you don't understand what your code is doing or why it does what it does, the answer is debugger.
Use the debugger to see what your code is doing. Just set a breakpoint and see your code performing, the debugger allow you to execute lines 1 by 1 and to inspect variables as it execute.

Debugger - Wikipedia, the free encyclopedia[^]

Mastering Debugging in Visual Studio 2010 - A Beginner's Guide[^]
Basic Debugging with Visual Studio 2010 - YouTube[^]
http://docs.oracle.com/javase/7/docs/technotes/tools/windows/jdb.html[^]
https://www.jetbrains.com/idea/help/debugging-your-first-java-application.html[^]
The debugger is here to show you what your code is doing and your task is to compare with what it should do.
There is no magic in the debugger, it don't find bugs, it just help you to. When the code don't do what is expected, you are close to a bug.

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