java 中System类

 public static void systemTest() {
        Map<String, String> getenv = System.getenv();
        for (Map.Entry<String, String> kvp : getenv.entrySet()) {
            System.out.println(String.format("环境变量：%S,值为:%s", kvp.getKey(), kvp
                    .getValue()));
        }
        System.out.println("properties属性：");
        Properties properties = System.getProperties();
        properties.list(System.out);

    }