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本文主要總結線程共享數據的相關知識，主要包括兩方面:一是某個線程內如何共享數據，保證各個線程的數據不交叉；一是多個線程間如何共享數據，保證數據的一致性。
自己實現的話，是定義一個Map,線程為鍵，數據為值,表中的每一項即是為每個線程準備的數據,這樣在一個線程中數據是一致的。
例子
package com.iot.thread;
import java.util.HashMap;
import java.util.Map;
import java.util.Random;
/**
* Created by brian on 2016/2/4.
*/
public class ThreadScopeShareData {
//準備一個哈希表，為每個線程準備數據
private static Map<Thread,Integer> threadData = new HashMap<>();
public static void main(String[] args) {
for (int i=0;i<2;i++){
new Thread(
new Runnable() {
@Override
public void run() {
int data = new Random().nextint();
threadData.put(Thread.currentThread(),data);
System.out.println(Thread.currentThread()+" put data："+data);
new A().get();
new B().get();
}
}
).start();
}
}
static class A{
public void get(){
int data = threadData.get(Thread.currentThread());
System.out.println("A from "+Thread.currentThread()+" get data "+data);
}
}
static class B{
public void get(){
int data = threadData.get(Thread.currentThread());
System.out.println("B from "+Thread.currentThread()+" get data "+data);
}
}
}
上述代碼偶爾會報異常：
Exception in thread "Thread-0" java.lang.NullPointerException
at com.iot.thread.ThreadScopeShareData$A.get(ThreadScopeShareData.java:29)
at com.iot.thread.ThreadScopeShareData$1.run(ThreadScopeShareData.java:21)
at java.lang.Thread.run(Thread.java:745)
具體原因還不知道
API:
java.lang:Class ThreadLocal<T>
使用ThreadLocal類型的對象代替上面的Map即可
定義一個對象來封裝多個變量，然后在ThreadLocal中存儲整個對象
多變量時，最好將ThreadLocal類放在數據類的內部，數據類采用單例模式，這樣，新建對象和獲取對象都會更方便，同時封裝性更強。
package com.iot.thread;
import java.util.Random;
/**
* Created by brian on 2016/2/4.
*/
public class ThreadLocalTest {
private static ThreadLocal<Integer> threadInger = new ThreadLocal<>();
public static void main(String[] args) {
for (int i=0;i<2;i++){
new Thread(new Runnable() {
@Override
public void run() {
int data = new Random().nextint(100);
threadInger.set(data);
System.out.println(Thread.currentThread()+" put data："+data);
MyThreadScopeData.getThreadInstance().setName(Thread.currentThread().toString());
MyThreadScopeData.getThreadInstance().setAge(data%10);
new A().get();
new B().get();
}
}
).start();
}
}
static class A{
public void get(){
int data = threadInger.get();
System.out.println("A from "+Thread.currentThread()+" get data "+data);
MyThreadScopeData myThreadScopeData = MyThreadScopeData.getThreadInstance();
System.out.println("A from "+myThreadScopeData);
}
}
static class B{
public void get(){
int data = threadInger.get();
System.out.println("B from "+Thread.currentThread()+" get data "+data);
MyThreadScopeData myThreadScopeData = MyThreadScopeData.getThreadInstance();
System.out.println("B from "+myThreadScopeData);
}
}
}
/**
* 將多變量封裝起來的數據類
* 單例模式，內置ThreadLocal類型變量
*/
class MyThreadScopeData{
private MyThreadScopeData(){
}
private static ThreadLocal<MyThreadScopeData> data = new ThreadLocal<>();
public static MyThreadScopeData getThreadInstance(){
MyThreadScopeData instance = data.get();
if(instance == null){
instance = new MyThreadScopeData();
data.set(instance);
}
return instance;
}
private String name;
private int age;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
@Override
public String toString() {
String reVal = super.toString()+"-{name,age}"+":{"+getName()+","+getAge()+"}";
return reVal;
}
}
幾種方式
最后一種方式的示例:
設計5個線程，其中三個線程每次對j增加1，另外兩個線程對j每次減少1
package com.iot.thread;
/**
* Created by brian on 2016/2/4.
*/
public class MutiThreadShareData {
private static MutiShareData mutiShareData = new MutiShareData();
public static void main(String[] args) {
for (int i=0;i<3;i++){
new Thread(
new Runnable() {
@Override
public void run() {
System.out.println(Thread.currentThread()+":{j from "+ mutiShareData.getJ()+" + to: "+mutiShareData.increment()+"}");
}
}
).start();
}
for (int i=0;i<2;i++){
new Thread(
new Runnable() {
@Override
public void run() {
System.out.println(Thread.currentThread()+":{j from "+ mutiShareData.getJ()+" - to: "+mutiShareData.decrement()+"}");
}
}
).start();
}
}
}
/**
* 將共享數據封裝在另一對象中（操作數據的方法也在該對象完成）
*/
class MutiShareData{
private int j = 0;
public synchronized int increment(){
return ++j;
}
public synchronized int decrement(){
return --j;
}
public synchronized int getJ() {
return j;
}
public synchronized void setJ(int j) {
this.j = j;
}
}
以上就是本文關于Java編程多線程之共享數據代碼詳解的全部內容，希望對大家有所幫助。感興趣的朋友可以繼續參閱本站其他相關專題，如有不足之處，歡迎留言指出。感謝朋友們對本站的支持！
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