集合去除元素

业务场景

集合A 包含 1，2，3，4，5 等数据
集合B 包含 2，6 数据
要求 剔除 集合A中B的重复数据

1.集合元素删除

List<String> moveList = new ArrayList<>();
moveList.add("5");
moveList.add("6");
List<String> allList = new ArrayList<>();
allList.add("1");
allList.add("2");
allList.add("3");
allList.add("4");
allList.add("5");
allList.add("6");
allList.add("9");
for (String move :moveList){
    for (String all: allList){
        if(move.equals(all)){
            allList.remove(all);
        }
    }
}
for (String n : allList){
    System.out.print(n+" ");
}

是不是看起来没什么问题。。。。
运行一下

Exception in thread "main" java.util.ConcurrentModificationException
at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:909)
at java.util.ArrayList$Itr.next(ArrayList.java:859)

ConcurrentModificationException 可以自行百度。不再赘述。

2.集合删除改造版本 iterator

public static void main(String[] args) {
        List<String> moveList = new ArrayList<>();
        moveList.add("5");
        moveList.add("6");
        List<String> allList = new ArrayList<>();
        allList.add("1");
        allList.add("2");
        allList.add("3");
        allList.add("4");
        allList.add("5");
        allList.add("6");
        allList.add("9");
        Iterator<String> iterator = allList.iterator();
        for (String move : moveList) {
            while (iterator.hasNext()){
                String next = iterator.next();
                if (next.equals(move)){
                    iterator.remove();
                    break;
                }
            }
        }
        for (String n : allList) {
            System.out.print(n + " ");
        }
    }

运行一下,搞定

1 2 3 4 9 
Process finished with exit code 0

3. 换一种写法 jdk1.8 流特性 Stream

static boolean isSame(List<String> list, String element){
    for (String l:list){
        if(element.equals(l)){
            return false;
        }
    }
    return true;
}

public static void main(String[] args) {
    List<String> moveList = new ArrayList<>();
    moveList.add("5");
    moveList.add("6");
    List<String> allList = new ArrayList<>();
    allList.add("1");
    allList.add("2");
    allList.add("3");
    allList.add("4");
    allList.add("5");
    allList.add("6");
    allList.add("9");
    Stream<String> stream = allList.stream();
    List<String> result = stream.filter(c -> isSame(moveList, c)).collect(Collectors.toList());
    for (String n : result) {
        System.out.print(n + " ");
    }

}

运行一下,搞定

1 2 3 4 9 
Process finished with exit code 0

同时，对于初始化集合优化

//Arrays.asList()
List<String> moveList = Arrays.asList("5","11");