多线程下java.util.ConcurrentModificationException问题解决

多线程同时增加和获取数据的情况：

import java.util.ArrayList;
import java.util.List;

public class Main {

    public static void main(String[] args) {
        new Main().test();
    }

    private List<String> mData = new ArrayList<>();
    private List<String> mCloneData;
    private int count = 0;

    public void test() {
        new Thread(new Runnable() {
            @Override
            public void run() {
                while (true) {
                    mData.add(count++ + "");
                    mCloneData = null;
                    try {
                        Thread.sleep(100);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }).start();

        new Thread(new Runnable() {
            @Override
            public void run() {
                while (true) {
                    for (String string : getData()) {
                        System.out.println(string);
                        try {
                            Thread.sleep(200);
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                    }
                }
            }
        }).start();
    }

    private List<String> getData() {
        if (mCloneData == null) {
            mCloneData = new ArrayList<>(mData);
        }
        return mCloneData;
    }
}

多线程同时增加、获取和删除数据的情况：

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class Main {

    public static void main(String[] args) {
        new Main().test();
    }

    private List<String> mData = new ArrayList<>();
    private List<String> mCloneData;
    private int count = 0;

    public void test() {
        new Thread(new Runnable() {
            @Override
            public void run() {
                while (true) {
                    synchronized (mData) {
                        mData.add(count++ + "");
                    }
                    mCloneData = null;
                    try {
                        Thread.sleep(100);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }

                }
            }
        }).start();

        new Thread(new Runnable() {
            @Override
            public void run() {
                while (true) {
                    for (String string : getData()) {
                        System.out.println(string);
                        try {
                            Thread.sleep(200);
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                    }
                }
            }
        }).start();

        new Thread(new Runnable() {
            @Override
            public void run() {
                while (true) {
                    synchronized (mData) {
                        Iterator<String> iterator = mData.iterator();
                        int i = 0;
                        while (iterator.hasNext()) {
                            String string = iterator.next();
                            int code = count - 1;
                            if (string.equals(code + "")) {
                                iterator.remove();
                            }
                            if (i < 5) {
                                try {
                                    Thread.sleep(100);
                                } catch (InterruptedException e) {
                                    e.printStackTrace();
                                }
                            }
                            i++;
                        }
                    }
                    try {
                        Thread.sleep(100);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }).start();
    }

    private List<String> getData() {
        if (mCloneData == null) {
            mCloneData = new ArrayList<>(mData);
        }
        return mCloneData;
    }
}

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参考链接：

java.util.ConcurrentModificationException 异常问题详解