安装java环境

1.从Internet下载jdk
2.安装步骤
       - Make the shell script executable
                % chmod +x j2sdk-1.4.2-03-linux-<ARCH>.bin
          (Replace <ARCH> with the architecture of your system, e.g.
          replace <ARCH> with i586 if your on an Intel system.)
        - Change to the directory you want to install into, e.g /usr/local
                % cd /usr/local
        - Extract the contents of the Java 2 SDK by running the shell script
                % ./j2sdk-1.4.2-03-linux-<ARCH>.bin
          (Replace <ARCH> with the architecture of your system, e.g.
          replace <ARCH> with i586 if your on an Intel system.)
  3.环境配置
      - Add j2sdk1.4.2/bin to PATH, e.g. if you installed into /usr/local
          编辑/etc/profile 文件－－－－对所有用户有效 ，添加
            export JAVA_HOME=/usr/local/j2sdk1.4.2
            export PATH=$PATH:$JAVA_HOME/bin:$JAVA_HOME/jre/bin
           export CLASSPATH=.:$JAVA_HOME/lib:$JAVA_HOME/jre/lib

   4. 测试
    写一个HelloWorld.java
public class HelloWorld
{
      public static void main(String[] args)
      {
            System.out.println("hello world in linux");
      }
}

javac HelloWorld.java
java HelloWorld
如果输出hello world in linux,表示成功安装java