Question

你好我怎样才能在我的列表开头添加一个元素method。

我知道我必须在这里创建一个新的Pokeball，将新的pokeball.next指向头部并指向新的Pokeball，但我不知道该怎么做

我的列表现在看起来像这样：

Bulbasaur -> Squirtle

我想在开头添加charmander

Charmander -> Bulbasaur -> Squirtle

调用方法时：d1.prepend(p3)，它必须通过Trainer类然后Pokeball类，就像我的addPokemon方法一样谢谢

public class test {
    public static void main(String[] args) {
        Pokemon p1 = new Pokemon("Bulbasaur", "grass");
        Pokemon p2 = new Pokemon("Squirtle", "water");
        Pokemon p3 = new Pokemon("Charmander", "fire");
        Trainer d1 = new Trainer("Pierre");
        d1.addPokemon(p1);
        d1.addPokemon(p2);
    }
}

public class Pokemon {
    private String name;
    private String type;
    private int niveau;

    public Pokemon(String name, String type) {
        this.name = name;
        this.type = type;
        this.niveau = (int) (Math.random() * (1 * 1 - 100) + 100);
    }
}

public class Trainer {

    public final String name;
    private Pokeball head;

    public Trainer(String name) {
        this.name = name;
    }

    public void addPokemon(Pokemon pok) {
        if (this.head != null) {
            this.head.addPokemon(pok);
        } else {
            this.head = new Pokeball(pok);
        }
    }

    public void prepend(Pokemon pok) {
        this.head.prepend(pok);
    }
}

public class Pokeball {

    private Pokemon pok;
    private Pokeball next;

    public Pokeball(Pokemon pok) {
        this.pok = pok;
    }

    public Pokeball(Pokemon pok, Pokeball next) {
        this.pok = pok;
        this.next = next;
    }

    public void addPokemon(Pokemon pok) {
        Pokeball current = this;
        while (current.next != null) {
            current = current.next;
        }
        current.next = new Pokeball(pok);
    }

    public void prepend(Pokemon pok) {

    }
}

Answer 1

除非每个prepend同时拥有对前一个Pokeball的引用，否则您无法致电Pokeball上的Pokeball附加内容。

解决方案实际上比这简单得多。只需将新Pokeball作为列表的首部：

public class Trainer {

        public final String name;
        private Pokeball head;

        ...

        public void prepend(Pokemon pok) {
           Pokeball newPokeball = new Pokeball(pok);
           newPokeball.next = this.head;
           this.head = newPokeball;
        }
    }

编辑：另一个有趣的练习是尝试在列表中间添加一个pokeball： Bulbasaur - ＆gt; Charmander - ＆gt;小水龟

要做到这一点，你只需要从头开始直到找到你想要添加新球的棒球。其余的与上面非常相似。

public void addAfterPokeball(Pokemon theOneToInsertAfter, Pokemon pok) {
           Pokeball newPokeball = new Pokeball(pok);
           Pokeball tmp = head;
           while (tmp != null && tmp.pok.name != theOneToInsertAfter.name) {
               tmp = tmp.next;
           }
           if (tmp!=null){
              newPokeball.next = tmp.next;
              tmp.next = newPokeball;
           } else {
             //could not find the pokeball to insert after
           }
        }

Answer 2

我们的馆藏课程将为您提供帮助。如果你创建一个Pokemon的LinkedList，这支持addFirst（）插入列表的头部。

List<Pokemon> list = new LinkedList<>();
//other pokemon inserted here 
// ...
//insert new item at front of list   
list.addFirst(newPokemon);

Answer 3

我试着猜猜你想做什么。我想你试图实现自己的链式列表。

您需要实例化一个Pokeball并将列表的当前第一个元素添加为您刚创建的实例的下一个元素。我猜你的List对象包含对你的第一个元素的引用，它也需要更改。

如何在链表的开头添加元素？

3 个答案: