java.util.ConcurrentModificationException

出现这个异常的情况有很多种

Exception in thread "main" java.util.ConcurrentModificationException    at java.util.Vector$Itr.checkForComodification(Vector.java:1184)    at java.util.Vector$Itr.next(Vector.java:1137)    at com.example.MyClass.test(MyClass.java:106)    at com.example.MyClass.main(MyClass.java:10)

下面是出异常的源代码

    public static void test() {        Vector<Model> vector = new Vector<>();        Vector<Model> vector1 = new Vector<>();        for (int i = 0; i < 50; i++) {            Model model = new Model();            model.setName("item" + i);            vector1.add(model);            vector.add(vector1.get(i));        }        Thread thread = new Thread(() -> {            for (int i = 0; i < 10; i++) {                if (i % 2 == 0) {                    try {                        Thread.sleep(1);                    } catch (InterruptedException e) {                        e.printStackTrace();                    }                    vector.remove(vector1.get(i));                    System.out.println(Thread.currentThread().getName() + "<------------->" + vector1.get(i).getName());                }            }        });        thread.setName("thread-test");        thread.start();        try {            Thread.sleep(1);        } catch (InterruptedException e) {            e.printStackTrace();        }        for (Model model : vector) {  //出现异常的位置            try {                Thread.sleep(1);            } catch (InterruptedException e) {                e.printStackTrace();            }            System.out.println(vector.size() + "<------------->" + model.getName());        }    }

因为foreach遍历集合的原理是通过Iterator迭代器实现遍历的，和以下代码类似

    Iterator<Model> iterator = vector.iterator();    while (iterator.hasNext()){        Model model = iterator.next();        System.out.println(vector.size() + "<------------->" + model.getName());    }

这里的iterator在一开始就拿到了，而后又通过thread-test线程删除了vector的某个元素，所以会出现java.util.ConcurrentModificationException

解决方法

使用fori循环就可以解决这个问题了

    for (int i = 0; i < vector.size(); i++) {        Model model = vector.get(i);        try {            Thread.sleep(1);        } catch (InterruptedException e) {            e.printStackTrace();        }        System.out.println(vector.size() + "<------------->" + model.getName());    }

运行看下效果：