HashMap原始碼詳解

成員變數

static

final
int default_initial_capacity = 1
<< 4; // aka 16
static
final
int maximum_capacity = 1
<< 30;// aka 2^30
static
final
float default_load_factor = 0.75f;
static
final
int treeify_threshold = 8;
static
final
int untreeify_threshold = 6;
static
final
int min_treeify_capacity = 64;
/* filed */
transient node table;//table為node鍊錶構建的陣列
transient set> entryset;
transient
int size;
transient
int modcount;
int threshold;
final
float loadfactor;//負載因子，預設值為0.75
//靜態內部類
static class nodeimplements map.entry
}

public

hashmap(int initialcapacity, float loadfactor) 
public
hashmap(int initialcapacity) 
public
hashmap()

public v put(k key, v value) 

final v putval(int hash, k key, v value, boolean onlyifabsent,
boolean evict) 
if (e.hash == hash &&
((k = e.key) == key || (key != null && key.equals(k))))
break;
p = e;}}
v oldvalue = e.value;
if (!onlyifabsent || oldvalue == null)
e.value = value;
afternodeaccess(e);
return oldvalue;}}
++modcount;
// 超過load factor*current capacity，resize
if (++size > threshold)
resize();
afternodeinsertion(evict);
return
null;
}final node resize() 
// 沒超過最大值，就擴充為原來的2倍
else
if ((newcap = oldcap << 1) < maximum_capacity &&
oldcap >= default_initial_capacity)
newthr = oldthr << 1; // double threshold
}else
if (oldthr > 0) // initial capacity was placed in threshold
newcap = oldthr;
else 
// 計算新的resize上限
if (newthr == 0) 
threshold = newthr;
@suppresswarnings()
node newtab = (node)new node[newcap];//建立table陣列
table = newtab;
if (oldtab != null) 
// 原索引+oldcap
else 
} while ((e = next) != null);
// 原索引放到bucket裡
if (lotail != null) 
// 原索引+oldcap放到bucket裡
if (hitail != null) }}
}}
return newtab;
}

public v get(object key) 

final nodegetnode(int hash, object key) while ((e = e.next) != null);}}
return
null;
}

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