linux安装jdk

JAVA_HOME=/usr/java/jdk1.7.0_71
JRE_HOME=/usr/java/jdk1.7.0_71/jre
PATH=$PATH:$JAVA_HOME/bin:$JRE_HOME/bin
CLASSPATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar:$JRE_HOME/lib
export JAVA_HOME JRE_HOME PATH CLASSPATH

public class Test {

        public static void main(String [] a)
        {
                System.out.println("hello world");
        }
}