本文主要總結(jié)線程共享數(shù)據(jù)的相關(guān)知識(shí)，主要包括兩方面:一是某個(gè)線程內(nèi)如何共享數(shù)據(jù)，保證各個(gè)線程的數(shù)據(jù)不交叉；一是多個(gè)線程間如何共享數(shù)據(jù)，保證數(shù)據(jù)的一致性。
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自己實(shí)現(xiàn)的話，是定義一個(gè)Map,線程為鍵，數(shù)據(jù)為值,表中的每一項(xiàng)即是為每個(gè)線程準(zhǔn)備的數(shù)據(jù),這樣在一個(gè)線程中數(shù)據(jù)是一致的。
例子
重慶分公司
重慶分公司
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(zhǔn)備一個(gè)哈希表，為每個(gè)線程準(zhǔn)備數(shù)據(jù)
private static Map 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(huì)報(bào)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
使用ThreadLocal類型的對(duì)象代替上面的Map即可
定義一個(gè)對(duì)象來封裝多個(gè)變量，然后在ThreadLocal中存儲(chǔ)整個(gè)對(duì)象
多變量時(shí)，最好將ThreadLocal類放在數(shù)據(jù)類的內(nèi)部，數(shù)據(jù)類采用單例模式，這樣，新建對(duì)象和獲取對(duì)象都會(huì)更方便，同時(shí)封裝性更強(qiáng)。
package com.iot.thread;
import java.util.Random;
/**
* Created by brian on 2016/2/4.
*/
public class ThreadLocalTest {
private static ThreadLocal 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(shù)據(jù)類
* 單例模式，內(nèi)置ThreadLocal類型變量
*/
class MyThreadScopeData{
private MyThreadScopeData(){
}
private static ThreadLocal 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(shè)計(jì)5個(gè)線程，其中三個(gè)線程每次對(duì)j增加1，另外兩個(gè)線程對(duì)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(shù)據(jù)封裝在另一對(duì)象中（操作數(shù)據(jù)的方法也在該對(duì)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(guān)于Java編程多線程之共享數(shù)據(jù)代碼詳解的全部?jī)?nèi)容，希望對(duì)大家有所幫助。感興趣的朋友可以繼續(xù)參閱本站其他相關(guān)專題，如有不足之處，歡迎留言指出。感謝朋友們對(duì)本站的支持！
