Java返回多个参数的方法

背景

• 在写代码的过程中，因有一些复杂的业务逻辑，需要返回多个结果。比如：需要增加一个true或者false，另外在加一个真正的结果值这样的类型。
• 可能会有人用到数组以及Map等作为结果返回，当然这样确实是可以完成这样的功能，但是并不是很优雅。

解决方案1

• 利用现有的轮子，或者自己造一个

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by FernFlower decompiler)
//

package reactor.util.function;

import java.io.Serializable;
import java.util.Arrays;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Objects;
import java.util.function.Function;
import reactor.util.annotation.NonNull;
import reactor.util.annotation.Nullable;

public class Tuple2<T1, T2> implements Iterable<Object>, Serializable {
    private static final long serialVersionUID = -3518082018884860684L;
    @NonNull
    final T1 t1;
    @NonNull
    final T2 t2;

    Tuple2(T1 t1, T2 t2) {
        this.t1 = Objects.requireNonNull(t1, "t1");
        this.t2 = Objects.requireNonNull(t2, "t2");
    }

    public T1 getT1() {
        return this.t1;
    }

    public T2 getT2() {
        return this.t2;
    }

    public <R> Tuple2<R, T2> mapT1(Function<T1, R> mapper) {
        return new Tuple2(mapper.apply(this.t1), this.t2);
    }

    public <R> Tuple2<T1, R> mapT2(Function<T2, R> mapper) {
        return new Tuple2(this.t1, mapper.apply(this.t2));
    }

    @Nullable
    public Object get(int index) {
        switch (index) {
            case 0:
                return this.t1;
            case 1:
                return this.t2;
            default:
                return null;
        }
    }

    public List<Object> toList() {
        return Arrays.asList(this.toArray());
    }

    public Object[] toArray() {
        return new Object[]{this.t1, this.t2};
    }

    public Iterator<Object> iterator() {
        return Collections.unmodifiableList(this.toList()).iterator();
    }

    public boolean equals(@Nullable Object o) {
        if (this == o) {
            return true;
        } else if (o != null && this.getClass() == o.getClass()) {
            Tuple2<?, ?> tuple2 = (Tuple2)o;
            return this.t1.equals(tuple2.t1) && this.t2.equals(tuple2.t2);
        } else {
            return false;
        }
    }

    public int hashCode() {
        int result = this.size();
        result = 31 * result + this.t1.hashCode();
        result = 31 * result + this.t2.hashCode();
        return result;
    }

    public int size() {
        return 2;
    }

    public final String toString() {
        return Tuples.tupleStringRepresentation(this.toArray()).insert(0, '[').append(']').toString();
    }
}

• 如果是三个参数

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by FernFlower decompiler)
//

package reactor.util.function;

import java.util.Objects;
import java.util.function.Function;
import reactor.util.annotation.NonNull;
import reactor.util.annotation.Nullable;

public class Tuple3<T1, T2, T3> extends Tuple2<T1, T2> {
    private static final long serialVersionUID = -4430274211524723033L;
    @NonNull
    final T3 t3;

    Tuple3(T1 t1, T2 t2, T3 t3) {
        super(t1, t2);
        this.t3 = Objects.requireNonNull(t3, "t3");
    }

    public T3 getT3() {
        return this.t3;
    }

    public <R> Tuple3<R, T2, T3> mapT1(Function<T1, R> mapper) {
        return new Tuple3(mapper.apply(this.t1), this.t2, this.t3);
    }

    public <R> Tuple3<T1, R, T3> mapT2(Function<T2, R> mapper) {
        return new Tuple3(this.t1, mapper.apply(this.t2), this.t3);
    }

    public <R> Tuple3<T1, T2, R> mapT3(Function<T3, R> mapper) {
        return new Tuple3(this.t1, this.t2, mapper.apply(this.t3));
    }

    @Nullable
    public Object get(int index) {
        switch (index) {
            case 0:
                return this.t1;
            case 1:
                return this.t2;
            case 2:
                return this.t3;
            default:
                return null;
        }
    }

    public Object[] toArray() {
        return new Object[]{this.t1, this.t2, this.t3};
    }

    public boolean equals(@Nullable Object o) {
        if (this == o) {
            return true;
        } else if (!(o instanceof Tuple3)) {
            return false;
        } else if (!super.equals(o)) {
            return false;
        } else {
            Tuple3 tuple3 = (Tuple3)o;
            return this.t3.equals(tuple3.t3);
        }
    }

    public int size() {
        return 3;
    }

    public int hashCode() {
        int result = super.hashCode();
        result = 31 * result + this.t3.hashCode();
        return result;
    }
}

• 以上都是来自这个包下面的，当然也可以自己去自定义

解决方案2

• 同样的，推荐第二种方案，就是利用 Apache的commons包下面的 MutableTriple<L, M, R> ,废话不多说，直接上截图：