class Parameter {
 private static ThreadLocal<Parameter> _parameter= new ThreadLocal<>();
 public static Parameter init() {
 _parameter.set(new Parameter());
 }
 public static Parameter get() {
 _parameter.get();
 }
 ...省略变量声明
}

class Entry extends WeakReference<ThreadLocal<?>> {
 Object value;
 Entry(ThreadLocal<?> k, Object v) {
 super(k);
 value = v;
 }
}

public void set(T value) {
 Thread t = Thread.currentThread();
 ThreadLocalMap map = getMap(t);
 if (map != null)
 map.set(this, value);
 else
 createMap(t, value);
}
ThreadLocalMap getMap(Thread t) {
 return t.threadLocals;
}

private void set(ThreadLocal<?> key, Object value) {
 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)]) {
 ThreadLocal<?> k = e.get();
 if (k == key) {
 e.value = value;
 return;
 }
 if (k == null) {
 replaceStaleEntry(key, value, i);
 return;
 }
 }
 tab[i] = new Entry(key, value);
 int sz = ++size;
 if (!cleanSomeSlots(i, sz) && sz >= threshold)
 rehash();
}

private static AtomicInteger nextHashCode = new AtomicInteger();
private static int nextHashCode() { 
 return nextHashCode.getAndAdd(HASH_INCREMENT);
}

private void resize() {
 Entry[] oldTab = table;
 int oldLen = oldTab.length;
 int newLen = oldLen * 2;
 Entry[] newTab = new Entry[newLen];
 int count = 0;
 for (int j = 0; j < oldLen; ++j) {
 Entry e = oldTab[j];
 if (e != null) {
 ThreadLocal<?> k = e.get();
 if (k == null) {
 e.value = null; // Help the GC
 } else {
 int h = k.threadLocalHashCode & (newLen - 1);
 while (newTab[h] != null)
 h = nextIndex(h, newLen);
 newTab[h] = e;
 count++;
 }
 }
 }
 setThreshold(newLen);
 size = count;
 table = newTab;
}

public T get() {
 Thread t = Thread.currentThread();
 ThreadLocalMap map = getMap(t);
 if (map != null) {
 ThreadLocalMap.Entry e = map.getEntry(this);
 if (e != null) {
 @SuppressWarnings("unchecked")
 T result = (T)e.value;
 return result;
 }
 }
 return setInitialValue();
}
private Entry getEntry(ThreadLocal<?> key) {
 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;
 while (e != null) {
 ThreadLocal<?> k = e.get();
 if (k == key)
 return e;
 if (k == null)
 expungeStaleEntry(i);
 else
 i = nextIndex(i, len);
 e = tab[i];
 }
 return null;
}