电脑上安装多个jdk

卸载

卸载已安装的JDK

删除注册表后 java -vesion 报错

直接把HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\这个注册表分支给删除了，然后到cmd下，运行java -version，出现另一个错误：

C:\Users>java -version
Error: opening registry key ‘Software\JavaSoft\Java Runtime Environment’
Error: could not find java.dll
Error: Could not find Java SE Runtime Environment.

解决方法：
Path系统环境变量中，把%JAVA_HOME%\bin调整到最前面

下载JDK

下载jdk 压缩包格式
如果注册表被删除
重新安装exe的jdk 从而重新生成注册表信息
只用安装jdk即可 jre不安装

配置环境变量

修改JAVA_HOME 指定修改版本

jmap -heap 报错

报出异常

Attaching to process ID 44995, please wait...
Error attaching to process: sun.jvm.hotspot.runtime.VMVersionMismatchException: Supported versions are 25.131-b11. Target VM is 25.161-b14
sun.jvm.hotspot.debugger.DebuggerException: sun.jvm.hotspot.runtime.VMVersionMismatchException: Supported versions are 25.131-b11. Target VM is 25.161-b14
        at sun.jvm.hotspot.HotSpotAgent.setupVM(HotSpotAgent.java:435)
        at sun.jvm.hotspot.HotSpotAgent.go(HotSpotAgent.java:305)
        at sun.jvm.hotspot.HotSpotAgent.attach(HotSpotAgent.java:140)
        at sun.jvm.hotspot.tools.Tool.start(Tool.java:185)
        at sun.jvm.hotspot.tools.Tool.execute(Tool.java:118)
        at sun.jvm.hotspot.tools.HeapSummary.main(HeapSummary.java:49)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at sun.tools.jmap.JMap.runTool(JMap.java:201)
        at sun.tools.jmap.JMap.main(JMap.java:130)
Caused by: sun.jvm.hotspot.runtime.VMVersionMismatchException: Supported versions are 25.131-b11. Target VM is 25.161-b14
        at sun.jvm.hotspot.runtime.VM.checkVMVersion(VM.java:227)
        at sun.jvm.hotspot.runtime.VM.<init>(VM.java:294)
        at sun.jvm.hotspot.runtime.VM.initialize(VM.java:370)
        at sun.jvm.hotspot.HotSpotAgent.setupVM(HotSpotAgent.java:431)