从ArrayList中删除项目时出错 [英] Error removing an item from an ArrayList

问题描述

我正在尝试使用线程从列表中删除一个值.但是代码失败并给出异常.请帮助我是线程编程的初学者.....

I'm trying to remove a value from the list using thread. But the code fails and gives an exception. Plz help I'm a beginner in thread programming.....

这是Test.java

import java.util.*;

public class Test {
    private static final List<Integer> Values = new ArrayList<Integer> ();
    public static void main(String args[]) {
        TestThread t1 = new TestThread(Values);
        t1.start();

        System.out.println(Values.size());
    }
}

这是TestThread.java

import java.util.*;

public class TestThread extends Thread {
    private final List<Integer> Values;

    public TestThread(List<Integer> v) {
        this.Values = v;
        Values.add(5);
    }

    public void run() {
        Values.remove(5);
        System.out.println("5 removed");
    }
}

推荐答案

此行的意思是:删除索引5处的值.但是索引5没有任何内容.

This line means: remove the value at index 5. But there's nothing in index 5.

    Values.remove(5);

当前数组中只有1个值，因为此行表示将值5添加到我的列表中，而不是将5个值添加到我的列表中.

There's only 1 value in the array currently because this line means add the value 5 into my list, not add 5 values to my list.

    Values.add(5);

您的错误很可能是IndexOutOfBoundsException.如果显示列表的大小，您会更清楚地看到它.

Your error is most likely IndexOutOfBoundsException. You'll see it more clearly if you display the size of your list.

public void run() {
    System.out.println(Values.size()); // should give you 1
    Values.remove(5);
    System.out.println("5 removed");
}

这是它的外观:

插入时，将5个自动装箱到Integer对象中.因此，要成功删除它，应将其包装为一个:new Integer(5).然后发出删除呼叫.然后，它将调用接受对象而不是int的remove的重载版本.

When it was inserted, 5 got auto-boxed into an Integer object. Thus, to successfully remove it, you should wrap it into one: new Integer(5). Then issue the remove call. It will then invoke the overloaded version of remove that accepts an Object, instead of the int.

Values.remove(new Integer(5));

表示从我的列表中删除名为"5"的Integer对象.

means Remove the Integer object named '5' from my list.

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