Write a Java program to count 1 to 1000 numbers using 10 threads?

Answer 1

// need a class to do customized counting
// (this can be a local class)
final class CounterThread extends Thread {

private final int rangeStart;
private final int rangeEnd;
private final int[] nums;
private int count;

private CounterThread(final int rangeStart, final int rangeEnd, final int[] nums) {
super();

this.rangeStart = rangeStart;
this.rangeEnd = rangeEnd;
this.nums = nums;

count = 0;

}

public void run() {
// actual counting process
for (int i = rangeStart; i <= rangeEnd; ++i) {
count += nums[i];

}

}

}

// define the number of ints we want to add up
final int ARRAY_SIZE = 1000;
// define the number of threads to use
final int NUM_THREADS = 10;
// define the number of ints each thread will add
final int NUMS_PER_ARRAY = ARRAY_SIZE / NUM_THREADS;

// NOTE: if ARRAY_SIZE is not evenly divisible by NUM_THREADS, then the
// code will need some tweaking to get the correct answer

int[] nums = new int[ARRAY_SIZE]; // assuming this is filled with numbers to count

// create our array of worker threads
CounterThread[] threads = new CounterThread[NUM_THREADS];
for (int i = 0; i < threads.length; ++i) {

// create the new thread which will count the given range
threads[i] = new CounterThread((i * NUMS_PER_ARRAY), (((i + 1) * NUMS_PER_ARRAY) - 1), nums);
// start the thread
threads[i].start();

}

// wait for all threads to finish
for (int i = 0; i < threads.length; ++i) {

threads[i].join();

}

// add up the individual counts from each thread
int totalCount = 0;
for (int i = 0; i < threads.length; ++i) {

totalCount += threads[i].count;

}

System.out.println(totalCount);

Answer 2

This is an example from The Java Tutorials on creating a "for" loop. They happen to use a program that counts 1 to 10 as an example.

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