Java：使用 .add(new Methodname()) 將一組字符串值添加到 ArrayList 中的每個元素

Question

我不確定我是否正確發布了問題，但問題就在這里。 我知道您可以向 ArrayList 的元素添加 String 或 int 值。 但我希望每個元素都是一組字符串名字、姓氏和關系值（理想情況下）。 我不知道這是否對 ArrayList 要求太多，但它會是理想的。

這是 ArrayList

ArrayList<Member> family = new ArrayList<Member>(); 
    family.add(new Member());
    family.add(new Member());
    family.add(new Member());
    family.add(new Member());

    for(Member dad : family){
        dad.setFirstName("Father");
        dad.setLastName("Last");
     }

    for(Member mom : family){
        mom.setFirstName("Mother");
        mom.setLastName("Last");
    }

    for(Member son : family){
        son.setFirstName("Son");
        son.setLastName("Last");
    }

    for(Member daughter : family){
        daughter.setFirstName("Daughter");
        daughter.setLastName("Last");
    }

Member 是用於獲取/設置這些值的類，以及用於在控制台上獲取輸出的覆蓋。

但是，當我打印到控制台時，我得到了一個完全錯誤的答案。 我得到了最后一個元素女兒的四次，每個四次：

[Member (firstname=Daughter, lastname=Last), Member (firstname=Daughter, lastname=Last), Member (firstname=Daughter, lastname=Last), Member (firstname=Daughter, lastname=Last)]
[Member (firstname=Daughter, lastname=Last), Member (firstname=Daughter, lastname=Last), Member (firstname=Daughter, lastname=Last), Member (firstname=Daughter, lastname=Last)]
[Member (firstname=Daughter, lastname=Last), Member (firstname=Daughter, lastname=Last), Member (firstname=Daughter, lastname=Last), Member (firstname=Daughter, lastname=Last)]
[Member (firstname=Daughter, lastname=Last), Member (firstname=Daughter, lastname=Last), Member (firstname=Daughter, lastname=Last), Member (firstname=Daughter, lastname=Last)]

是什么賦予了？

順便說一句，這是我用來打印的：

    @Override
public String toString() {
    return "Member (firstname=" + firstname + ", lastname=" + lastname + ")";
}

Answer 1

代碼中的每個下一個for循環都會重置上一個在您的family列表中更新的值。 這就是為什么您的列表只有上次迭代設置的值。