java long 空判断_Long类型null判断带值判断，null必须写在最前面

BEGIN;

验证代码如下：

public static void main(String[] args) {

Long id = null;

System.out.println(test1(id));

System.out.println(test2(id));

System.out.println(test3(id));

System.out.println(test4(id));

}

private static String test1(Long id) {

try {

if(0 == id || null == id) return “test1 --> 判断代码成功。”;

else return “test1 --> 判断代码错误！”;

} catch (Exception e) {

return “test1 --> Exception”;

}

}

private static String test2(Long id) {

try {

if(id == 0 || null == id) return “test2 --> 判断代码成功。”;

else return “test2 --> 判断代码错误！”;

} catch (Exception e) {

return “test2 --> Exception”;

}

}

private static String test3(Long id) {

try {

if(null