JDK升级操作

sudo yum install java-1.8.0-openjdk-devel.x86_64
修改/etc/profile --编辑用户目录下(root用户的目录为/root)的.bashrc或.profile文件。如果你想在所有用户的shell下都生效，就编辑/etc/profile文件。
JAVA_HOME=/usr/lib/jvm/java-openjdk
source /etc/profile

JDK升级后，jmap等命令无法使用

报错

Heap Usage:
Exception in thread "main" java.lang.reflect.InvocationTargetException
  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: java.lang.RuntimeException: unknown CollectedHeap type : class sun.jvm.hotspot.gc_interface.CollectedHeap
  at sun.jvm.hotspot.tools.HeapSummary.run(HeapSummary.java:157)
  at sun.jvm.hotspot.tools.Tool.startInternal(Tool.java:260)
  at sun.jvm.hotspot.tools.Tool.start(Tool.java:223)
  at sun.jvm.hotspot.tools.Tool.execute(Tool.java:118)
  at sun.jvm.hotspot.tools.HeapSummary.main(HeapSummary.java:50)
  ... 6 more