JAVA集合篇之LinkedHashSet底层源码(JDK8)

LinkedHashSet的图表如下：

LinkedHashSet是HashSet的子类，底层实现为：数组+双向链表。

LinkedHashSet也具有去重功能，并且元素是有序的。

构造方法如下：

执行空构造

LinkedHashSet<Object> hashSet = new LinkedHashSet<>();

分析：

/**
 * Constructs a new, empty linked hash set with the default initial
 * capacity (16) and load factor (0.75).
 */
public LinkedHashSet() {
    super(16, .75f, true); //调用父类(HashSet)的构造器
}

创建了一个LinkedHashMap，初始容量16，加载因子0.75

HashSet(int initialCapacity, float loadFactor, boolean dummy) {
        map = new LinkedHashMap<>(initialCapacity, loadFactor);
    }

public LinkedHashMap(int initialCapacity, float loadFactor) {
        super(initialCapacity, loadFactor);
        accessOrder = false;
    }

public HashMap(int initialCapacity, float loadFactor) {
        if (initialCapacity < 0)
            throw new IllegalArgumentException("Illegal initial capacity: " +
                                               initialCapacity);
        if (initialCapacity > MAXIMUM_CAPACITY)
            initialCapacity = MAXIMUM_CAPACITY;
        if (loadFactor <= 0 || Float.isNaN(loadFactor))
            throw new IllegalArgumentException("Illegal load factor: " +
                                               loadFactor);
        this.loadFactor = loadFactor;
        this.threshold = tableSizeFor(initialCapacity); //这里计算出来=16
    }

调用 hashSet.add(123); 添加元素，会执行以下方法，底层也是走的hashMap的put方法

public boolean add(E e) {
    return map.put(e, PRESENT)==null;
}

// 以下方法的添加逻辑同上一篇博客，这里略过

/**
 * Implements Map.put and related methods
 *
 * @param hash hash for key
 * @