面试专题--并发篇代码

package day02.leetcode; import java.util.concurrent.atomic.AtomicInteger; import java.util.concurrent.locks.Condition; import java.util.concurrent.locks.ReentrantLock; public class T1195 { public static void main(String[] args) { FizzBuzz fb = new FizzBuzz3(30); new Thread(fb::fizz).start(); new Thread(fb::buzz).start(); new Thread(fb::fizzbuzz).start(); new Thread(fb::number).start(); } static interface FizzBuzz { public void fizz(); public void buzz(); public void fizzbuzz(); public void number(); } // 事先计算好每个 i 该打印什么, 用 1,2,3,4 区分, 用乐观锁检查条件 static class FizzBuzz3 implements FizzBuzz { private final int n; private final int[] array; private AtomicInteger i = new AtomicInteger(); public FizzBuzz3(int n) { this.n = n; this.array = new int[n]; for (int i = 1; i <= n; i++) { if (i % 3 == 0 && i % 5 != 0) { array[i - 1] = 1; } else if (i % 3 != 0 && i % 5 == 0) { array[i - 1] = 2; } else if (i % 3 == 0) { array[i - 1] = 3; } else { array[i - 1] = 4; } } } @Override public void fizz() { out: while (i.get() < n) { while (true) { int i = this.i.get(); if (i >= n) { break out; } if (array[i] == 1) { break; } Thread.yield(); } System.out.println("fizz"); i.incrementAndGet(); } } @Override public void buzz() { out: while (i.get() < n) { while (true) { int i = this.i.get(); if (i >= n) { break out; } if (array[i] == 2) { break; } Thread.yield(); } System.out.println("buzz"); i.incrementAndGet(); } } @Override public void fizzbuzz() { out: while (i.get() < n) { while (true) { int i = this.i.get(); if (i >= n) { break out; } if (array[i] == 3) { break; } Thread.yield(); } System.out.println("fizzbuzz"); i.incrementAndGet(); } } @Override public void number() { out: while (i.get() < n) { while (true) { int i = this.i.get(); if (i >= n) { break out; } if (array[i] == 4) { break; } Thread.yield(); } System.out.println(i.get() + 1); i.incrementAndGet(); } } } // 用多个条件变量精确控制唤醒, 性能较其他版本更佳 static class FizzBuzz2 implements FizzBuzz { private final int n; private int i = 1; private final ReentrantLock lock = new ReentrantLock(); private final Condition c1 = lock.newCondition(); private final Condition c2 = lock.newCondition(); private final Condition c3 = lock.newCondition(); private final Condition c4 = lock.newCondition(); public FizzBuzz2(int n) { this.n = n; } @Override public void fizz() { while (i <= n) { lock.lock(); try { if (i % 3 == 0 && i % 5 != 0) { System.out.println("fizz"); i++; if (i % 3 != 0 && i % 5 == 0) { c2.signal(); } else if (i % 3 == 0 && i % 5 == 0) { c3.signal(); } else { c4.signal(); } if (i == n) { c2.signal(); c3.signal(); c4.signal(); } } else { try { c1.await(); } catch (InterruptedException e) { e.printStackTrace(); } } } finally { lock.unlock(); } } } @Override public void buzz() { while (i <= n) { lock.lock(); try { if (i % 3 != 0 && i % 5 == 0) { System.out.println("buzz"); i++; if (i % 3 == 0 && i % 5 == 0) { c3.signal(); } else if (i % 3 != 0 && i % 5 != 0) { c4.signal(); } else { c1.signal(); } if (i == n) { c1.signal(); c3.signal(); c4.signal(); } } else { try { c2.await(); } catch (InterruptedException e) { e.printStackTrace(); } } } finally { lock.unlock(); } } } @Override public void fizzbuzz() { while (i <= n) { lock.lock(); try { if (i % 3 == 0 && i % 5 == 0) { System.out.println("fizzbuzz"); i++; if (i % 3 != 0 && i % 5 != 0) { c4.signal(); } else if (i % 3 == 0 && i % 5 != 0) { c1.signal(); } else { c2.signal(); } if (i == n) { c1.signal(); c2.signal(); c4.signal(); } } else { try { c3.await(); } catch (InterruptedException e) { e.printStackTrace(); } } } finally { lock.unlock(); } } } @Override public void number() { while (i <= n) { lock.lock(); try { if (i % 3 != 0 && i % 5 != 0) { System.out.println(i); i++; if (i % 3 == 0 && i % 5 != 0) { c1.signal(); } else if (i % 3 != 0 && i % 5 ==