JDKソース--CopyOnWriteArraySet

一、概念
クラス定義:

public class CopyOnWriteArraySet extends AbstractSet
        implements java.io.Serializable 

AbstractSetクラスを継承し、Setインタフェースを実現し、Set共通の操作のセットを持つ.

はSerializableインタフェースを実現し、シーケンス化することができる.

特徴:

は空の要素を許可します.

重複要素はありません.

スレッドは安全です.

二、使用

//TestCopyOnWriteArraySet
public class TestCopyOnWriteArraySet {
    private static final String TAG = "CopyOnWriteArraySet";
    private CopyOnWriteArraySet set = new CopyOnWriteArraySet();

    public void testAdd() {
        set.add(null);
        set.add("AAA");
        set.add("BBB");
        set.add("CCC");
        set.add("CCC");
        Log.d(TAG, "zwm, add set: " + set);
    }

    public void testRemove() {
        set.remove("AAA");
        Log.d(TAG, "zwm, remove set: " + set);
    }

    public void testContains() {
        Log.d(TAG, "zwm, contains BBB: " + set.contains("BBB"));
    }

    public void testIterator() {
        Iterator iterator = set.iterator();
        while (iterator.hasNext()) {
            Log.d(TAG, "zwm, iterator item: " + iterator.next());
        }
    }

    public void testSize() {
        Log.d(TAG, "zwm, size: " + set.size());
    }
}

//    
private void testMethod() {
    Log.d(TAG, "zwm, testMethod");
    TestCopyOnWriteArraySet testCopyOnWriteArraySet = new TestCopyOnWriteArraySet();
    testCopyOnWriteArraySet.testAdd();
    testCopyOnWriteArraySet.testContains();
    testCopyOnWriteArraySet.testRemove();
    testCopyOnWriteArraySet.testSize();
    testCopyOnWriteArraySet.testIterator();
}

//  log
2019-08-17 14:31:41.940 zwm, testMethod
2019-08-17 14:31:41.941 zwm, add set: [null, AAA, BBB, CCC]
2019-08-17 14:31:41.941 zwm, contains BBB: true
2019-08-17 14:31:41.942 zwm, remove set: [null, BBB, CCC]
2019-08-17 14:31:41.942 zwm, size: 3
2019-08-17 14:31:41.942 zwm, iterator item: null
2019-08-17 14:31:41.942 zwm, iterator item: BBB
2019-08-17 14:31:41.942 zwm, iterator item: CCC

三、原理
重要なパラメータ

//           CopyOnWriteArrayList
private final CopyOnWriteArrayList al;

コンストラクタ

//      ，  CopyOnWriteArrayList          
public CopyOnWriteArraySet() {
    al = new CopyOnWriteArrayList();
}

//  Collection           ，  CopyOnWriteArrayList     Collection       
public CopyOnWriteArraySet(Collection extends E> c) {
    if (c.getClass() == CopyOnWriteArraySet.class) {
        @SuppressWarnings("unchecked") CopyOnWriteArraySet cc =
            (CopyOnWriteArraySet)c;
        al = new CopyOnWriteArrayList(cc.al);
    }
    else {
        al = new CopyOnWriteArrayList();
        al.addAllAbsent(c);
    }
}

public boolean add(E e)

//      
public boolean add(E e) {
    return al.addIfAbsent(e); //  CopyOnWriteArrayList addIfAbsent  
}

public boolean remove(Object o)

//     o     
public boolean remove(Object o) {
    return al.remove(o); //  CopyOnWriteArrayList remove  
}

public boolean contains(Object o)

//         o     
public boolean contains(Object o) {
    return al.contains(o); //  CopyOnWriteArrayList contains  
}

public Iterator iterator()

//       
public Iterator iterator() {
    return al.iterator(); //  CopyOnWriteArrayList iterator  
}

public int size()

//      
public int size() {
    return al.size(); //  CopyOnWriteArrayList size  
}

四、テーマ
CopyOnWriteArrayList