22Java对象的内存图

￡神魔★判官ぃ 2024-05-01 16:18 42阅读 0赞

**目录**

一个对象的内存图

两个对象的内存图

两个引用指向同一个对象

--------------------

## 一个对象的内存图 ##

实例代码：

![705afc3f3c2d44189d7d19cc4f0c13e4.png][]

创建对象时：

Student s = new Student（）；

内存中执行以下操作：

1．加载class文件（student这个类的字节码文件加载到方法区中）

![0d9ce6a21d294c72bb62bd05cbfa09ab.png][]

2．申明局部变量（对s进行声明）

![9a81f68f886f4f59b5a4a0cb6a8f3ce9.png][]

3．在堆内存中开辟一个空间（new关键字）

![9e0f3128a4e34b3999e764d9e843bc5e.png][]

4．默认初始化

![5eb662f825c04ef58bc313cb724bbe36.png][]

5．显示初始化

如果代码中给出赋值，则会覆盖默认初始化。如果没有赋值，则不需要显示初始化

![b525c429c8924b0fb1c472f4aa224496.png][]

6. 构造方法初始化（4.5.6.步都是在堆中刚开辟的空间进行初始化）

Student s = new Student（）；也没有参数，可以忽略初始化

7．将堆内存中的地址值赋值给左边的局部变量

![f382f1d75fff4bd280e9283c42221dde.png][]

![19e19964961043628dbac6ee56d6c43b.png][]

![58fa269f7c3342e0bf675e3c62f1e965.png][]

![ff95e8d3534742789c53f48af80c8cf4.png][]

![ab989c22709546478b3fd9daa92d969d.png][]

程序结束

方法和main函数依次出栈，main函数中的所有变量也会消失

![30daf1b80a574d1e956e0841e193f8a2.png][]

![718d761add3f444aa29bb47cce43e80f.png][]

针对某个对象，没有变量指向这个对象/空间，这个空间也会消失

![5e57129cab224241bd05fa4a63eedb3e.png][]

## 两个对象的内存图 ##

与一个对象的内存图类似，一下简略截图：

实例代码：

![f2b5fb11a0894961b3b6ba931f5367af.png][]

![b4da080ae53145958593d37bdc80aa7d.png][]

![c3e4e399cf9f49dbb2191c3dd686d78e.png][]

第二次创建对象时，不需要再次加载.class文件

![001b93de35094510b88152cc31ef5e70.png][]

![c76e80e1e30940fbb84a525be0afade3.png][]

![0f5cb29be61a4bfc806e575d75a4abdc.png][]

![eda61f392f8b4f1982daf03affe7a28c.png][]

## 两个引用指向同一个对象 ##

![185331b6f5514215accef87f42d8aadc.png][]

![9adb972be0c540a3aeda7ae2d0a2d98b.png][]

![d057b19178914ade8a3f10a82ff1fc74.png][]

![4e92141e9ce447ac9de42a8188c464fc.png][]

![739c6f41ea054ec7a4f2d74b11fcd7a4.png][]

![236c2b0420b0437aae4785638e3f3f80.png][]

null覆盖了地址001

![62fb751daa054479ac66d9e4a251ff2e.png][]

指针异常

![a4cd8582def0418f9f5ba8f36655b2cd.png][]

stu2正常

![fb49932edfc94bc8aab943396fcbf688.png][]

如果stu2地址也用null覆盖，对象空间变成垃圾值

[705afc3f3c2d44189d7d19cc4f0c13e4.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/05/01/5341158730c144e8b8fc008f81bf9330.png
[0d9ce6a21d294c72bb62bd05cbfa09ab.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/05/01/70121570f36d47ce8adbba06af721dd7.png
[9a81f68f886f4f59b5a4a0cb6a8f3ce9.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/05/01/a1180cc24ff9495c93c1807d5ff2bc84.png
[9e0f3128a4e34b3999e764d9e843bc5e.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/05/01/9b424fcdae074b5aafcc1a0594a2ced3.png
[5eb662f825c04ef58bc313cb724bbe36.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/05/01/77e4c40980724d74bf7b67b7c87404f2.png
[b525c429c8924b0fb1c472f4aa224496.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/05/01/ad9461927795430a99358af3bcb03f8c.png
[f382f1d75fff4bd280e9283c42221dde.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/05/01/067ba9f2f27149e88a7e5a43b57b2b57.png
[19e19964961043628dbac6ee56d6c43b.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/05/01/f14d5dc4970e49cb94eb191a17796868.png
[58fa269f7c3342e0bf675e3c62f1e965.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/05/01/84f5bd5f7a9c4c27b75059b2bae97fa9.png
[ff95e8d3534742789c53f48af80c8cf4.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/05/01/3444217a042349da9b6d305b49ecfcf9.png
[ab989c22709546478b3fd9daa92d969d.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/05/01/3bbd7ba8166043129aea722dfd7c5191.png
[30daf1b80a574d1e956e0841e193f8a2.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/05/01/5d3212ce15ae43f4a33db27757edf0ff.png
[718d761add3f444aa29bb47cce43e80f.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/05/01/0d736d80bea9492083f0302d028d5df2.png
[5e57129cab224241bd05fa4a63eedb3e.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/05/01/e7ef66a3a61644698376e2b8e3af7dd2.png
[f2b5fb11a0894961b3b6ba931f5367af.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/05/01/2f4cdbeffa9e449f97e99a7e347fbfae.png
[b4da080ae53145958593d37bdc80aa7d.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/05/01/74f0f38a03854130a542a159e93f0609.png
[c3e4e399cf9f49dbb2191c3dd686d78e.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/05/01/590cbed117434a5291a04af147d3cc68.png
[001b93de35094510b88152cc31ef5e70.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/05/01/dab38c75bccf45e59857c2e76f41704d.png
[c76e80e1e30940fbb84a525be0afade3.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/05/01/47669d12ebe94a81a4d5b0fcbdde00b8.png
[0f5cb29be61a4bfc806e575d75a4abdc.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/05/01/c6dd407774974747af82c8afebe14b69.png
[eda61f392f8b4f1982daf03affe7a28c.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/05/01/e774007dd0cf497d805add5fb8b79bd4.png
[185331b6f5514215accef87f42d8aadc.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/05/01/6972cb06357f434ca1cf17f869e53bf8.png
[9adb972be0c540a3aeda7ae2d0a2d98b.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/05/01/a051014876b24320aa8113fb390db024.png
[d057b19178914ade8a3f10a82ff1fc74.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/05/01/86010d0f93d64cbca7e0309aea6f6461.png
[4e92141e9ce447ac9de42a8188c464fc.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/05/01/a8e8f57cc9d44560815aebec88d59856.png
[739c6f41ea054ec7a4f2d74b11fcd7a4.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/05/01/e6c5df8d8f254843b733ff3a2d66e631.png
[236c2b0420b0437aae4785638e3f3f80.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/05/01/bc5b2d4c34ae40c88a99e3e68458f8c3.png
[62fb751daa054479ac66d9e4a251ff2e.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/05/01/596315cd65594f75a05b583948ba60ba.png
[a4cd8582def0418f9f5ba8f36655b2cd.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/05/01/aa9aca3421fc458787f28d6a57b83657.png
[fb49932edfc94bc8aab943396fcbf688.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/05/01/226d6a755b5a42e681b9311f0858cf10.png