Question

java 多线程访问数组求和？

有两个数组
int[] input={100,5,98,77,60,88,36};
int[] output={0,0,0,0,0,0,0};
例如：如果取input的100，那么就是计算1+。。。+100=5050；要把得到的这个值放到output的第一个数组元素中，要input跟output要一一对应，用3到5个线程，写出。
请写具体，谢谢！

Answer 1

public class T
{
 int[] input={100,5,98,77,60,88,36};  
 int[] output={0,0,0,0,0,0,0};  
 int curr = 0;
 
 public synchronized int getCurr() {
  if( curr== input.length )
   return -1;
  return curr++;
 }
 
 
 static class Worker extends Thread
 {
  T t;
  public Worker(T t) {
   this.t = t;
  }
  
  public void run() {
   int idx; 
   while( (idx=t.getCurr()) != -1 ) {
    int sum = 0;
    for(int i=0; i<t.input[idx]; i++ ) {
     sum += i;
    }
    t.output[idx] = sum;
   }
   System.out.println( getName() + " over" );
  }
 }
 

 public static void main(String[] args) throws Exception{
  T t = new T();
  Thread t1 = new Worker(t);
  Thread t2 = new Worker(t);
  Thread t3 = new Worker(t);
  t1.start();
  t2.start();
  t3.start();
  t1.join();
  t2.join();
  t3.join();
  for(int i=0; i<t.output.length; i++) {
   System.out.print( t.output[i] + "," );
  }
  System.out.println();
 }
}

追问

这个for循环要改成
for(int i=0; i<=t.input[idx]; i++ ) {
sum += i;
}
呵呵！
谢谢！
给力！

Answer 2

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51

public class T
{
int[] input={100,5,98,77,60,88,36};
int[] output={0,0,0,0,0,0,0};
int curr = 0;

public synchronized int getCurr() {
if( curr== input.length )
return -1;
return curr++;
}

static class Worker extends Thread
{
T t;
public Worker(T t) {
this.t = t;
}

public void run() {
int idx;
while( (idx=t.getCurr()) != -1 ) {
int sum = 0;
for(int i=0; i<t.input[idx]; i++ ) {
sum += i;
}
t.output[idx] = sum;
}
System.out.println( getName() + " over" );
}
}

public static void main(String[] args) throws Exception{
T t = new T();
Thread t1 = new Worker(t);
Thread t2 = new Worker(t);
Thread t3 = new Worker(t);
t1.start();
t2.start();
t3.start();
t1.join();
t2.join();
t3.join();
for(int i=0; i<t.output.length; i++) {
System.out.print( t.output[i] + "," );
}
System.out.println();
}
}