一、用法

ThreadLocal用于保存某個(gè)線(xiàn)程共享變量：對(duì)于同一個(gè)static ThreadLocal，不同線(xiàn)程只能從中g(shù)et，set，remove自己的變量，而不會(huì)影響其他線(xiàn)程的變量。

ThreadLocal.get: 獲取ThreadLocal中當(dāng)前線(xiàn)程共享變量的值。

ThreadLocal.set: 設(shè)置ThreadLocal中當(dāng)前線(xiàn)程共享變量的值。

ThreadLocal.remove: 移除ThreadLocal中當(dāng)前線(xiàn)程共享變量的值。

ThreadLocal.initialValue: ThreadLocal沒(méi)有被當(dāng)前線(xiàn)程賦值時(shí)或當(dāng)前線(xiàn)程剛調(diào)用remove方法后調(diào)用get方法，返回此方法值。

package?com.coshaho.reflect;public?class?MyThreadLocal{private?static?final?ThreadLocal<Object> threadLocal =?new?ThreadLocal<Object>(){//ThreadLocal沒(méi)有被當(dāng)前線(xiàn)程賦值時(shí)或當(dāng)前線(xiàn)程剛調(diào)用remove方法后調(diào)用get方法，返回此方法值@Overrideprotected?Object initialValue(){System.out.println("調(diào)用get方法時(shí)，當(dāng)前線(xiàn)程共享變量沒(méi)有設(shè)置，調(diào)用initialValue獲取默認(rèn)值！");return?null;}};public?static?void?main(String[] args){new?Thread(new?MyIntegerTask("IntegerTask1")).start();new?Thread(new?MyStringTask("StringTask1")).start();new?Thread(new?MyIntegerTask("IntegerTask2")).start();new?Thread(new?MyStringTask("StringTask2")).start();}public?static?class?MyIntegerTask?implements?Runnable{private?String name;MyIntegerTask(String name){this.name = name;}@Overridepublic?void?run(){for(int?i =?0; i <?5; i++){// ThreadLocal.get方法獲取線(xiàn)程變量if(null?== MyThreadLocal.threadLocal.get()){// ThreadLocal.et方法設(shè)置線(xiàn)程變量MyThreadLocal.threadLocal.set(0);System.out.println("線(xiàn)程"?+ name +?": 0");}else{int?num = (Integer)MyThreadLocal.threadLocal.get();MyThreadLocal.threadLocal.set(num +?1);System.out.println("線(xiàn)程"?+ name +?": "?+ MyThreadLocal.threadLocal.get());if(i ==?3){MyThreadLocal.threadLocal.remove();}}try{Thread.sleep(1000);}catch?(InterruptedException e){e.printStackTrace();}}??}?}public?static?class?MyStringTask?implements?Runnable{private?String name;MyStringTask(String name){this.name = name;}@Overridepublic?void?run(){for(int?i =?0; i <?5; i++){if(null?== MyThreadLocal.threadLocal.get()){MyThreadLocal.threadLocal.set("a");System.out.println("線(xiàn)程"?+ name +?": a");}else{String str = (String)MyThreadLocal.threadLocal.get();MyThreadLocal.threadLocal.set(str +?"a");System.out.println("線(xiàn)程"?+ name +?": "?+ MyThreadLocal.threadLocal.get());}try{Thread.sleep(800);}catch?(InterruptedException e){e.printStackTrace();}}}} }

運(yùn)行結(jié)果如下：

調(diào)用get方法時(shí)，當(dāng)前線(xiàn)程共享變量沒(méi)有設(shè)置，調(diào)用initialValue獲取默認(rèn)值！ 線(xiàn)程IntegerTask1: 0 調(diào)用get方法時(shí)，當(dāng)前線(xiàn)程共享變量沒(méi)有設(shè)置，調(diào)用initialValue獲取默認(rèn)值！ 線(xiàn)程IntegerTask2: 0 調(diào)用get方法時(shí)，當(dāng)前線(xiàn)程共享變量沒(méi)有設(shè)置，調(diào)用initialValue獲取默認(rèn)值！ 調(diào)用get方法時(shí)，當(dāng)前線(xiàn)程共享變量沒(méi)有設(shè)置，調(diào)用initialValue獲取默認(rèn)值！ 線(xiàn)程StringTask1: a 線(xiàn)程StringTask2: a 線(xiàn)程StringTask1: aa 線(xiàn)程StringTask2: aa 線(xiàn)程IntegerTask1: 1 線(xiàn)程IntegerTask2: 1 線(xiàn)程StringTask1: aaa 線(xiàn)程StringTask2: aaa 線(xiàn)程IntegerTask2: 2 線(xiàn)程IntegerTask1: 2 線(xiàn)程StringTask2: aaaa 線(xiàn)程StringTask1: aaaa 線(xiàn)程IntegerTask2: 3 線(xiàn)程IntegerTask1: 3 線(xiàn)程StringTask1: aaaaa 線(xiàn)程StringTask2: aaaaa 調(diào)用get方法時(shí)，當(dāng)前線(xiàn)程共享變量沒(méi)有設(shè)置，調(diào)用initialValue獲取默認(rèn)值！ 線(xiàn)程IntegerTask2: 0 調(diào)用get方法時(shí)，當(dāng)前線(xiàn)程共享變量沒(méi)有設(shè)置，調(diào)用initialValue獲取默認(rèn)值！ 線(xiàn)程IntegerTask1: 0

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