15.2.1 一个元组类库

最新推荐文章于 2022-07-08 11:06:57 发布

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最新推荐文章于 2022-07-08 11:06:57 发布

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本文链接：https://blog.youkuaiyun.com/weixin_33669968/article/details/88889796

本文介绍了一种使用Java泛型实现的元组类结构，从二元组到五元组，展示了如何创建泛型类并实例化。通过具体示例，解释了泛型在方法返回类型中的应用，以及如何在不同类型的组合中使用这些元组。

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public class TwoTuple<A, B> {

    public final A first;
    public final B second;

    public TwoTuple(A a, B b) {
        first = a;
        second = b;
    }

    @Override
    public String toString() {
        return "TwoTuple{" +
                "first=" + first +
                ", second=" + second +
                '}';
    }

}

public class ThreeTuple<A, B, C> extends TwoTuple<A, B> {

    public final C third;

    public ThreeTuple(A a, B b, C c) {
        super(a, b);
        third = c;
    }

    @Override
    public String toString() {
        return "ThreeTuple{" +
                "third=" + third +
                ", first=" + first +
                ", second=" + second +
                '}';
    }
}

public class FourTuple<A, B, C, D> extends ThreeTuple<A, B, C> {

    public final D fourth;

    public FourTuple(A a, B b, C c, D d) {
        super(a, b, c);
        fourth = d;
    }

    @Override
    public String toString() {
        return "FourTuple{" +
                "fourth=" + fourth +
                ", third=" + third +
                ", first=" + first +
                ", second=" + second +
                '}';
    }
}

public class FiveTuple<A, B, C, D, E> extends FourTuple<A, B, C, D> {

    public final E fifth;

    public FiveTuple(A a, B b, C c, D d, E e) {
        super(a, b, c, d);
        fifth = e;
    }

    @Override
    public String toString() {
        return "FiveTuple{" +
                "fifth=" + fifth +
                ", fourth=" + fourth +
                ", third=" + third +
                ", first=" + first +
                ", second=" + second +
                '}';
    }
}

public class Amphibian {
}

public class Vehicle {
}

1）方法的返回类型是泛型，方法的参数列表中没有泛型，故方法的返回值前不需要泛型参数列表；

public class TupleTest {

    static TwoTuple<String, Integer> f() {
        return new TwoTuple<String, Integer>("hi", 47);
    }

    static ThreeTuple<Amphibian, String, Integer> g() {
        return new ThreeTuple<Amphibian, String, Integer>(
                new Amphibian(), "hi", 47);
    }

    static FourTuple<Vehicle, Amphibian, String, Integer> h() {
        return new FourTuple<Vehicle, Amphibian, String, Integer>(
                new Vehicle(), new Amphibian(), "hi", 47);
    }

    static FiveTuple<Vehicle, Amphibian, String, Integer, Double> k() {
        return new FiveTuple<Vehicle, Amphibian, String, Integer, Double>(
                new Vehicle(), new Amphibian(), "hi", 47, 11.1);
    }

    public static void main(String[] args) {
        TwoTuple<String, Integer> ttsi = f();
        System.out.println(ttsi);

        System.out.println(g());
        System.out.println(h());
        System.out.println(k());
    }

}

输出

TwoTuple{first=hi, second=47}
ThreeTuple{third=47, first=chapter15._2._1.Amphibian@610455d6, second=hi}
FourTuple{fourth=47, third=hi, first=chapter15._2._1.Vehicle@511d50c0, second=chapter15._2._1.Amphibian@60e53b93}
FiveTuple{fifth=11.1, fourth=47, third=hi, first=chapter15._2._1.Vehicle@5e2de80c, second=chapter15._2._1.Amphibian@1d44bcfa}