java

安装sun jdk 的方法

卸载centos7 自带的jdk
    rpm -qa | grep java
    java-1.8.0-openjdk-headless-1.8.0.101-3.b13.el7_2.x86_64
    javapackages-tools-3.4.1-11.el7.noarch
    tzdata-java-2016f-1.el7.noarch
    java-1.8.0-openjdk-1.8.0.101-3.b13.el7_2.x86_64
    python-javapackages-3.4.1-11.el7.noarch     
    rpm -e --nodeps java-1.8.0-openjdk-1.8.0.101-3.b13.el7_2.x86_64
    rpm -e --nodeps java-1.8.0-openjdk-headless-1.8.0.101-3.b13.el7_2.x86_64

查看class 的编译版本

javap -verbose ServiceImpl.class
J2SE 8 = 52,
J2SE 7 = 51,
J2SE 6.0 = 50,
J2SE 5.0 = 49,
JDK 1.4 = 48,
JDK 1.3 = 47,
JDK 1.2 = 46,
JDK 1.1 = 45