1、get()方法
（1）获取当前用的线程，并找到线程关联的threadLocalMap
（2）threadLocalMap为空则进行初始化一个新的并返回
（3）threadLocalMap不为空则根据threadlocal作为key查找Entry
（4）若Entry不为空则返回entry对应的值，否则执行第二条
public T get() {
// 获取当前线程
Thread t = Thread.currentThread();
ThreadLocalMap map = getMap(t);
//若当前线程关联的ThreadLocal不为空则查询
if (map != null) {
//根据threadLocal查询对应的Entry
ThreadLocalMap.Entry e = map.getEntry(this);
if (e != null) {
@SuppressWarnings("unchecked")
T result = (T)e.value;
return result;
}
}
return setInitialValue();
}
private T setInitialValue() {
//默认返回null值
T value = initialValue();
Thread t = Thread.currentThread();
ThreadLocalMap map = getMap(t);
//如果当前调用线程关联的ThreadLocalMap为空则创建，否则设置值进去
if (map != null)
map.set(this, value);
else
//new ThreadLocalMap(this,value)
createMap(t, value);
return value;
}
private Entry getEntry(ThreadLocal<?> key) {
//根据key获取其在数组的下标位置
int i = key.threadLocalHashCode & (table.length - 1);
Entry e = table[i];
if (e != null && e.get() == key)
return e;
else
return getEntryAfterMiss(key, i, e);
}
private Entry getEntryAfterMiss(ThreadLocal<?> key, int i, Entry e) {
Entry[] tab = table;
int len = tab.length;
//数组下标的Entry不为空且关联的threadlocal与查找的threadlocal不一致
while (e != null) {
ThreadLocal<?> k = e.get();
//entry关联的threadlocal与查找的相等则直接返回
if (k == key)
return e;
if (k == null)
//关联的threadlocal为空，则触发清理key为null的Entry并重新进行rehash旧Entry数组的元素
//threadLocalMap的hash冲突与hashMap的冲突处理方式不一致，hashMap使用的是链表地址法，
//而threadLocalMap使用的开放地址法——线性探测，即顺序查找下一位置或者遍历全表，效率较低
expungeStaleEntry(i);
else
//递增下标i的值进行下一轮的查找
i = nextIndex(i, len);
e = tab[i];
}
return null;
}2、remove()方法
（1）获取当前用的线程，并找到线程关联的threadLocalMap
（2）若不为空则删除threadLocalMap中关联的值，否则啥也不做
//ThreadLocal
public void remove() {
ThreadLocalMap m = getMap(Thread.currentThread());
if (m != null)
//删除当前threadLocal对象关联的Entry
m.remove(this);
}
//ThreadLocalMap
private void remove(ThreadLocal<?> key) {
Entry[] tab = table;
int len = tab.length;
int i = key.threadLocalHashCode & (len-1);
for (Entry e = tab[i];
e != null;
e = tab[i = nextIndex(i, len)]) {
if (e.get() == key) {
e.clear();
expungeStaleEntry(i);
return;
}
}
}以上是java中ThreadLocal核心方法怎么使用的详细内容。更多信息请关注PHP中文网其他相关文章！
