HashMap构造函数有哪些

hashMap有4个构造函数：

public HashMap(int initialCapacity, float loadFactor)

public HashMap(int initialCapacity)

public HashMap()

public HashMap(Map<? extends K, ? extends V> m)

 

/*** Constructs an empty <tt>HashMap</tt> with the specified initial* capacity and load factor.** @param initialCapacity the initial capacity* @param loadFactor the load factor* @throws IllegalArgumentException if the initial capacity is negative* or the load factor is nonpositive*/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);}/*** Constructs an empty <tt>HashMap</tt> with the specified initial* capacity and the default load factor (0.75).** @param initialCapacity the initial capacity.* @throws IllegalArgumentException if the initial capacity is negative.*/public HashMap(int initialCapacity) {this(initialCapacity, DEFAULT_LOAD_FACTOR);}/*** Constructs an empty <tt>HashMap</tt> with the default initial capacity* (16) and the default load factor (0.75).*/public HashMap() {this.loadFactor = DEFAULT_LOAD_FACTOR; // all other fields defaulted }/*** Constructs a new <tt>HashMap</tt> with the same mappings as the* specified <tt>Map</tt>. The <tt>HashMap</tt> is created with* default load factor (0.75) and an initial capacity sufficient to* hold the mappings in the specified <tt>Map</tt>.** @param m the map whose mappings are to be placed in this map* @throws NullPointerException if the specified map is null*/public HashMap(Map<? extends K, ? extends V> m) {this.loadFactor = DEFAULT_LOAD_FACTOR;putMapEntries(m, false);}

 

转载于:https://www.cnblogs.com/hujinshui/p/9950077.html

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