需求：因为特殊原因要改变jdk版本
第一步：卸载之前的Java
方法1.用杀毒软件卸载
方法2.用JavaUninstallTool卸载
链接：https://pan.baidu.com/s/1yJWo-gMq6bd-7SwsubdINg
提取码：na84
原因：不卸载的话，Java还是原来的版本，用Java -version的时候可以看到
第二步：下载jre的资源（自己网上找）并一键安装（注意安装的位置）
原因：为了安装新版本的Java
第三步：找到jdk的位置，并改系统环境变量
- 控制面板所有控制面板项系统-->高级系统设置-->环境变量
- 新建JAVA_HOME项，修改值为jdk目录比如：C:Program FilesJavajdk1.6.0_45
- 新建CLASSPATH项，修改值为：（一定要加点和分号，表示一直都是这个home）.;%JAVA_HOME%lib;%JAVA_HOME%lib ools.jar
- 在path项里面的编辑中，最后面加入一串值：（如果前面有冒号可以不用加）;%JAVA_HOME%in;%JAVA_HOME%jrein;
相关解答：
前面说的都做了但是还没有成功怎么办？——重启电脑
（建议不要删注册表）卸载时候真的想要删Javasoft的注册表：创建一个以.bat结尾的文件内容如下，并运行。
reg query hklmsoftwareclassesinstallerproducts /f "java" /s | find "HKEY_LOCAL_MACHINE" > deljava.txt
for /f "tokens=* delims= " %%a in (deljava.txt) do reg delete %%a /f
del deljava.txt
reg delete "HKEY_LOCAL_MACHINESOFTWAREJavaSoftJava Runtime Environment" /f
reg delete "HKEY_LOCAL_MACHINESOFTWAREwow6432nodeJavaSoftJava Runtime Environment" /f
非要查看Javasoft的注册表：Windows + R ，regedit ， 计算机HKEY_LOCAL_MACHINESOFTWARE...里面有你想要的
把Javasoft错删怎么办，希望下面这个可以帮助你参考
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINESOFTWAREJavaSoft]
[HKEY_LOCAL_MACHINESOFTWAREJavaSoftAuto Update]
"AUVersion"="2.0.5.1"
[HKEY_LOCAL_MACHINESOFTWAREJavaSoftJava Development Kit]
"CurrentVersion"="1.5"
[HKEY_LOCAL_MACHINESOFTWAREJavaSoftJava Development Kit1.5]
"JavaHome"="1"
"MicroVersion"="0"
[HKEY_LOCAL_MACHINESOFTWAREJavaSoftJava Development Kit1.5.0_11]
"JavaHome"="1"
"MicroVersion"="0"
[HKEY_LOCAL_MACHINESOFTWAREJavaSoftJava Plug-in]
[HKEY_LOCAL_MACHINESOFTWAREJavaSoftJava Plug-in1.5.0_11]
"JavaHome"="C:\Program Files\Java\jre1.5.0_11"
"UseJava2IExplorer"=dword:00000001
"HideSystemTrayIcon"=dword:00000000
[HKEY_LOCAL_MACHINESOFTWAREJavaSoftJava Plug-in1.6.0_26]
"JavaHome"="C:\Program Files\Java\jre6"
"UseJava2IExplorer"=dword:00000001
"UseNewJavaPlugin"=dword:00000001
"HideSystemTrayIcon"=dword:00000000
[HKEY_LOCAL_MACHINESOFTWAREJavaSoftJava Runtime Environment]
"CurrentVersion"="1.6"
"Java6FamilyVersion"="1.6.0_26"
[HKEY_LOCAL_MACHINESOFTWAREJavaSoftJava Runtime Environment1.5]
"JavaHome"="C:\Program Files\Java\jre1.5.0_11"
"RuntimeLib"="C:\Program Files\Java\jre1.5.0_11\bin\client\jvm.dll"
"MicroVersion"="0"
[HKEY_LOCAL_MACHINESOFTWAREJavaSoftJava Runtime Environment1.5.0_11]
"JavaHome"="C:\Program Files\Java\jre1.5.0_11"
"MicroVersion"="0"
"RuntimeLib"="C:\Program Files\Java\jre1.5.0_11\bin\client\jvm.dll"
[HKEY_LOCAL_MACHINESOFTWAREJavaSoftJava Runtime Environment1.5.0_11MSI]
"INSTALLDIR"="C:\Program Files\Java\jre1.5.0_11\"
"SYSTRAY"="1"
"EULA"="0"
"IEXPLORER"="1"
"MOZILLA"="0"
"JAVAUPDATE"="1"
"AUTOUPDATECHECK"="1"
"JU"="1"
[HKEY_LOCAL_MACHINESOFTWAREJavaSoftJava Runtime Environment1.6]
"JavaHome"="C:\Program Files\Java\jre6"
"RuntimeLib"="C:\Program Files\Java\jre6\bin\client\jvm.dll"
"MicroVersion"="0"
[HKEY_LOCAL_MACHINESOFTWAREJavaSoftJava Runtime Environment1.6.0_26]
"JavaHome"="C:\Program Files\Java\jre6"
"MicroVersion"="0"
"RuntimeLib"="C:\Program Files\Java\jre6\bin\client\jvm.dll"
[HKEY_LOCAL_MACHINESOFTWAREJavaSoftJava Runtime Environment1.6.0_26MSI]
"JU"="1"
"OEMUPDATE"=""
"MODE"="C"
"JQS"=""
"FROMVERSION"="NA"
"FROMVERSIONFULL"=""
"KERNEL"=""
"PRODUCTVERSION"="6.0.260"
"INSTALLDIR"="C:\Program Files\Java\jre6\"
"SYSTRAY"="1"
"EULA"="0"
"IEXPLORER"="1"
"MOZILLA"="1"
"JAVAUPDATE"="1"
"AUTOUPDATECHECK"="1"
"AUTOUPDATEDELAY"=""
"ImageCkSum"="2251778205"
"FullVersion"="1.6.0_26-b03"
[HKEY_LOCAL_MACHINESOFTWAREJavaSoftJava Update]
[HKEY_LOCAL_MACHINESOFTWAREJavaSoftJava UpdatePolicy]
"EnableJavaUpdate"=dword:00000001
"NotifyDownload"=dword:00000001
"NotifyInstall"=dword:00000000
"PostStatusUrl"="https://sjremetrics.java.com/b/ss//6"
"Country"="CN"
[HKEY_LOCAL_MACHINESOFTWAREJavaSoftJava Web Start]
"CurrentVersion"="1.6.0_26"
[HKEY_LOCAL_MACHINESOFTWAREJavaSoftJava Web Start1.0.1]
"Home"="C:\Program Files\Java\jre6\bin"
[HKEY_LOCAL_MACHINESOFTWAREJavaSoftJava Web Start1.0.1_02]
"Home"="C:\Program Files\Java\jre6\bin"
[HKEY_LOCAL_MACHINESOFTWAREJavaSoftJava Web Start1.0.1_03]
"Home"="C:\Program Files\Java\jre6\bin"
[HKEY_LOCAL_MACHINESOFTWAREJavaSoftJava Web Start1.0.1_04]
"Home"="C:\Program Files\Java\jre6\bin"
[HKEY_LOCAL_MACHINESOFTWAREJavaSoftJava Web Start1.2]
"Home"="C:\Program Files\Java\jre6\bin"
[HKEY_LOCAL_MACHINESOFTWAREJavaSoftJava Web Start1.2.0_01]
"Home"="C:\Program Files\Java\jre6\bin"
[HKEY_LOCAL_MACHINESOFTWAREJavaSoftJava Web Start1.5.0_11]
"Home"="C:\Program Files\Java\jre1.5.0_11\bin"
[HKEY_LOCAL_MACHINESOFTWAREJavaSoftJava Web Start1.6.0_26]
"Home"="C:\Program Files\Java\jre6\bin"
[HKEY_LOCAL_MACHINESOFTWAREJavaSoftPrefs]