java - 如何在链表的开头添加元素？

你好，我怎样做一个method，在列表的开头添加一个元素。

我知道我必须在这里创建一个新的Pokeball，将new pokeball.next指向该头部，然后将头部指向新的Pokeball，但是我不知道该怎么做

我的清单现在看起来像这样：

Bulbasaur -> Squirtle

我想在开头添加charmander

Charmander -> Bulbasaur -> Squirtle

调用方法：d1.prepend(p3)时，它必须先经过Trainer类，然后再经过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) {

    }
}

最佳答案

除非每个prepend都拥有对先前Pokeball的引用，否则无法在Pokeball上调用Pokeball在其后附加内容。

解决方案实际上比这简单得多。只需将新的Pokeball放在列表的开头即可：

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-> Charmander->松鼠

为此，您只需要从头开始，直到找到要在其后添加新球的pokeball。其余与上面非常相似。

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
           }
        }