序
這塊內容網上一搜一大片,但還是自己的理解和親身測驗更靠譜一些。
引用傳遞1
public class Demo {
public static void main(String[] args) {
Person per = new Person("01", "UUUUU");
changePer(per);
System.out.println(per);
}
private static void changePer(Person per) {
per.setName("UIASUIAS");
}
}
結果:
Person{id='01', name='UIASUIAS'}
Process finished with exit code 0
顯然,這是引用傳遞,另外解釋一下JVM,方法區存在的是這個person 的描述(也可稱之爲一個模型),new person()的實例對象存在堆內存中,堆中可以存在多個person的實例。
引用傳遞2
public class Demo {
public static void main(String[] args) {
ArrayList<Person> list = new ArrayList<>();
Person per = new Person("01", "UUUUU");
list.add(per);
System.out.println(JSON.toJSONString(list));
per.setName("PPPPPPPPp");
System.out.println(JSON.toJSONString(list));
change(list);
System.out.println(JSON.toJSONString(list));
}
public static void change(ArrayList<Person> list){
list.get(0).setName("TTTT");
}
}
結果:
[{"id":"01","name":"UUUUU"}]
[{"id":"01","name":"PPPPPPPPp"}]
[{"id":"01","name":"TTTT"}]
Process finished with exit code 0
顯然2,不僅在list.add()後修改list中的對象爲引用傳遞,把list當做參數傳給方法也爲引用傳遞,list.get(0)還是獲得了main方法裏person的引用地址
引用傳遞3
public static void main(String[] args) {
ArrayList<Person> list = new ArrayList<>();
Person per = new Person("01", "UUUUU");
list.add(per);
ArrayList<Person> list1 = new ArrayList<>();
list1.addAll(list);
System.out.println(JSON.toJSONString(list1));
per.setName("PPPPPPPPp");
System.out.println(JSON.toJSONString(list1));
}
結果:
[{"id":"01","name":"UUUUU"}]
[{"id":"01","name":"PPPPPPPPp"}]
Process finished with exit code 0
顯然3,這個也是引用傳遞