program arguments，vm arguments，environment variable

作者：david_zhang@sh 【转载时请以超链接形式标明文章】

https://www.cnblogs.com/david-zhang-index/p/16846493.html

参数太多，傻傻分不清楚，简单说

1，program arguments是main函数args[]参数

2，vm arguments是java环境变量

3，environment variable是jvm环境变量

看代码如何获取这些参数：

public class TestProgram {
    public static void main(String[] args) {
        // program arguments对应的args参数
        for (String arg : args) {
            System.out.println(arg);
        }
        System.out.println("==============program arguments对应的args参数===============");
        System.out.println();

        // getProperty()获取java的环境变量
        String value1 = System.getProperty("key1");
        String value2 = System.getProperty("key2");
        System.out.println("System.getProperty(\"key1\")----->" + value1);
        System.out.println("System.getProperty(\"key2\")----->" + value2);
        Properties properties = System.getProperties();
        System.out.println("System.getProperties():=======>" + properties);
        System.out.println("==============getProperty()获取java的环境变量===============");
        System.out.println();


        // 获取运行jvm环境变量
        System.getenv();
        Map<String, String> getenv = System.getenv();
        System.out.println("System.getenv():----->" + getenv);
        String env1 = System.getenv("env1");
        String env2 = System.getenv("env2");
        System.out.println("System.getenv(\"env1\")=======>" + env1);
        System.out.println("System.getenv(\"env2\")=======>" + env2);
        System.out.println("===============获取运行jvm环境变量===============");
        System.out.println();
    }
}

-argu=111
-arge=222
==============program arguments对应的args参数===============

System.getProperty("key1")----->v1
System.getProperty("key2")----->v2

==============getProperty()获取java的环境变量===============

System.getenv("env1")=======>test
System.getenv("env2")=======>prod
==============获取运行jvm环境变量===============

参数设置

 总结：

System.getProperty();

System.getProperties();

System.getenv();