Mon, 01 Jan 0001 00:00:00 +0000

Intro(HashMap) #

hello hashmap
- 构造器 #
```
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
}
```
- 初始容量 #
  
  实际是求取一个整形数值的最接近 \({\color{red}2^{n}}\) 的值。
  
  可以通过以下方法获取：
  \(2^{0} < x <= 2^{1}-1\) \(\hspace{5em} [00000000\quad00000000\quad00000000\quad0000000{\color{red}1}] - [00000000\quad00000000\quad00000000\quad0000000{\color{red}1}]\)
  \(2^{1} < x <= 2^{2}-1\) \(\hspace{5em} [00000000\quad00000000\quad00000000\quad000000{\color{red}10}] - [00000000\quad00000000\quad00000000\quad000000{\color{red}11}]\)
  \(2^{2} < x <= 2^{3}-1\) \(\hspace{5em} [00000000\quad00000000\quad00000000\quad00000{\color{red}100}] - [00000000\quad00000000\quad00000000\quad00000{\color{red}111}]\)
  \(2^{3} < x <= 2^{4}-1\) \(\hspace{5em} [00000000\quad00000000\quad00000000\quad0000{\color{red}1000}] - [00000000\quad00000000\quad00000000\quad0000{\color{red}1111}]\)
  \(2^{4} < x <= 2^{5}-1\) \(\hspace{5em} [00000000\quad00000000\quad00000000\quad000{\color{red}10000}] - [00000000\quad00000000\quad00000000\quad000{\color{red}11111}]\)
  \(\hspace{2.5em}\vdots\)
  \(2^{28} < x <= 2^{29}-1\) \(\hspace{4.3em} [000{\color{red}10000\quad00000000\quad00000000\quad00000000}] - [000{\color{red}11111\quad11111111\quad11111111\quad11111111}]\)
  \(2^{29} < x <= 2^{30}-1\) \(\hspace{4.3em} [00{\color{red}100000\quad00000000\quad00000000\quad00000000}] - [00{\color{red}111111\quad11111111\quad11111111\quad11111111}]\)
  \(2^{30} < x <= 2^{31}-1\) \(\hspace{4.3em} [0{\color{red}1000000\quad00000000\quad00000000\quad00000000}] - [0{\color{red}1111111\quad11111111\quad11111111\quad11111111}]\)

archive

Intro(HashMap) #

构造器 #

初始容量 #