获取所有环境变量的键值

import java.util.Map;

public class TestEnv {

    public static void main(String[] args) {
        Map<String, String> envMap = System.getenv();
        for (String key: envMap.keySet()) {
            System.out.printf("%s : %s\n", key, envMap.get(key));
        }
    }
}

运行结果示例：

PATH : /usr/local/bin:/usr/bin
LESS : -R
LC_CTYPE : 
LS_COLORS : di=34;
HOME : /Users/letian

获取特定的环境变量

public class TestEnv {

    public static void main(String[] args) {
        String value = System.getenv("HOME");
        System.out.println(value);
    }
}