Question

我有一个方法返回一个带有两个arraylists的对象：

return new Object[] {work, play};

我试图让他们以另一种方法退出。我已经尝试转换为ArrayList但是我得到错误'数组需要，但java.lang.Object找到'。

ArrayList setWork = (ArrayList)obj[0];
ArrayList setPlay = (ArrayList)obj[1];

创建ArrayList的完整代码：

public static Object[] getWorkandPlay(ArrayList al) {

    ArrayList work = new ArrayList();
    ArrayList play = new ArrayList();

    for (int i=0; i<al.size(); i++){
        String item = (String) al.get(i);

        if (item.startsWith("w.")) {
            System.out.println("w " + item);
            work.add(item);
        } else if (item.startsWith("p.")) {
            System.out.println("p " + item);
            play.add(item);
        } else {
            System.out.println("Entries must start with either w. or p.\n");
        }
    }
    return new Object[] {work, play};
}

Answer 1

return new Object [] {work，play};我认为返回一个对象数组。尝试ArrayList result = new ArrayList（）; 将工作和结果放在结果中然后返回结果。然后

Answer 2

在您的调用代码中，您应该将obj的引用类型设置为Object数组。你可能有代码中的Object obj = getWorkandPlay(anArrayList);。将其更改为Object[] obj = getWorkandPlay(anArrayList);。

Answer 3

我根据你的代码做了类似的事情并且它有效...

class Test{
    public static Object[] getWorkandPlay(ArrayList al) {
        ArrayList work = new ArrayList();
        ArrayList play = new ArrayList();

        for (int i=0; i<al.size(); i++){
            String item = (String) al.get(i);

            if (item.startsWith("w.")) {
                System.out.println("w " + item);
                work.add(item);
            } else if (item.startsWith("p.")) {
                System.out.println("p " + item);
                play.add(item);
            } else {
                System.out.println("Entries must start with either w. or p.\n");
            }
        }
        return new Object[] {work, play};
    }
    public static void main(String[] args) {
        ArrayList<String> al=new ArrayList<>();
        al.add("w. test");
        al.add("p. test");
        Object[] obj=getWorkandPlay(al);
        ArrayList setWork = (ArrayList)obj[0];
        ArrayList setPlay = (ArrayList)obj[1];
    }
}

输出

w w. test
p p. test

Answer 4

您的代码中某处可能有拼写错误。这为我编译：

import java.util.*;

public class SampleClass {

    public static void main(String[] args) {
        // Create an ArrayList and add some sample Strings
        ArrayList al = new ArrayList();
        al.add("w. test");
        al.add("p. test");

        Object[] obj = getWorkandPlay(al);

        ArrayList setWork = (ArrayList)obj[0];
        ArrayList setPlay = (ArrayList)obj[1];
    }

    public static Object[] getWorkandPlay(ArrayList al) {
        ArrayList work = new ArrayList();
        ArrayList play = new ArrayList();

        for (int i=0; i<al.size(); i++){
            String item = (String) al.get(i);

            if (item.startsWith("w.")) {
                System.out.println("w " + item);
                work.add(item);
            } else if (item.startsWith("p.")) {
                System.out.println("p " + item);
                play.add(item);
            } else {
                System.out.println("Entries must start with either w. or p.\n");
            }
        }

        return new Object[] {work, play};
    }
}

从Object获取ArrayList

4 个答案: