两个线程循环打印奇偶数
题目要求：两个线程循环打印奇偶数。
1.示例1：
输入：7
输出：
OddThread: 1
EvenThread: 2
OddThread: 3
EvenThread: 4
OddThread: 5
EvenThread: 6
OddThread: 7
2.示例2：
输入：5
输出：
OddThread: 1
EvenThread: 2
OddThread: 3
EvenThread: 4
OddThread: 5
附代码：
一、方法一：ReentrantLock + Condition
class PrintOddEven { // 成员变量（字段），用于存储对象状态，在整个类中都可以使用 // 表示当前要打印的数字，是从1开始打印 private int num = 1; // 表示结尾数字 private final int max; // 可重入锁 private final ReentrantLock lock = new ReentrantLock(); // 创建一个与该锁绑定的等待队列oddCondition，用于管理线程的等待和唤醒 private final Condition oddCondition = lock.newCondition(); // 奇数线程的等待队列 private final Condition evenCondition = lock.newCondition(); // 偶数线程的等待队列 public PrintOddEven(int max) { // 构造方法参数，用于从外部接收传入的值 this.max = max; // 把参数的值赋给成员变量 } // 奇数线程 public void printOdd() { while (num <= max) { // 循环没超过最大值的时候才打印 lock.lock(); // 获取锁 try { if (num % 2 != 0) { // 如果是奇数 // 打印该奇数 System.out.println(Thread.currentThread().getName() + ": " + num); num++; // 唤醒偶数线程 evenCondition.signal(); } // 如果是偶数 else { // 奇数线程等待 oddCondition.await(); } // 捕获await()线程在等待期间，其他线程调用interrupt()抛出的InterruptedException异常 } catch (InterruptedException e) { Thread.currentThread().interrupt(); } finally { lock.unlock(); } } } public void printEven() { while (num <= max) { lock.lock(); try { if (num % 2 == 0) { System.out.println(Thread.currentThread().getName() + ": " + num); num++; oddCondition.signal(); } else { evenCondition.await(); } } catch (InterruptedException e) { Thread.currentThread().interrupt(); } finally { lock.unlock(); } } } }二、方法二：Synchronized + wait/notify
class PrintOddEven { private int num = 1; private final int max; private final Object lock = new Object(); public PrintOddEven(int max) { this.max = max; } public void printOdd() { synchronized (lock) { while (num <= max) { if (num % 2 != 0) { System.out.println(Thread.currentThread().getName() + ": " + num); num++; lock.notify(); } else { try { lock.wait(); } catch (InterruptedException e) { Thread.currentThread().interrupt(); } } } } } public void printEven() { synchronized (lock) { while (num <= max) { if (num % 2 == 0) { System.out.println(Thread.currentThread().getName() + ": " + num); num++; lock.notify(); } else { try { lock.wait(); } catch (InterruptedException e) { Thread.currentThread().interrupt(); } } } } } }三、方法三：使用信号量 Semaphore（最简洁）
class PrintOddEven { private int num = 1; private final int max; private final Semaphore oddSemaphore = new Semaphore(1); private final Semaphore evenSemaphore = new Semaphore(0); public PrintOddEven(int max) { this.max = max; } public void printOdd() { while (num <= max) { try { oddSemaphore.acquire(); if (num <= max) { System.out.println(Thread.currentThread().getName() + ": " + num); num++; } evenSemaphore.release(); } catch (InterruptedException e) { Thread.currentThread().interrupt(); } } } public void printEven() { while (num <= max) { try { evenSemaphore.acquire(); if (num <= max) { System.out.println(Thread.currentThread().getName() + ": " + num); num++; } oddSemaphore.release(); } catch (InterruptedException e) { Thread.currentThread().interrupt(); } } } }ACM模式：
一、方法一：ReentrantLock + Condition
import java.util.Scanner; import java.util.concurrent.locks.Condition; import java.util.concurrent.locks.ReentrantLock; class PrintOddEven { // 成员变量（字段），用于存储对象状态，在整个类中都可以使用 // 表示当前要打印的数字，是从1开始打印 private int num = 1; // 表示结尾数字 private final int max; // 可重入锁 private final ReentrantLock lock = new ReentrantLock(); // 创建一个与该锁绑定的等待队列oddCondition，用于管理线程的等待和唤醒 private final Condition oddCondition = lock.newCondition(); // 奇数线程的等待队列 private final Condition evenCondition = lock.newCondition(); // 偶数线程的等待队列 public PrintOddEven(int max) { // 构造方法参数，用于从外部接收传入的值 this.max = max; // 把参数的值赋给成员变量 } // 奇数线程 public void printOdd() { while (num <= max) { // 循环没超过最大值的时候才打印 lock.lock(); // 获取锁 try { if (num % 2 != 0) { // 如果是奇数 // 打印该奇数 System.out.println(Thread.currentThread().getName() + ": " + num); num++; // 唤醒偶数线程 evenCondition.signal(); } // 如果是偶数 else { // 奇数线程等待 oddCondition.await(); } // 捕获await()线程在等待期间，其他线程调用interrupt()抛出的InterruptedException异常 } catch (InterruptedException e) { Thread.currentThread().interrupt(); } finally { lock.unlock(); } } } public void printEven() { while (num <= max) { lock.lock(); try { if (num % 2 == 0) { System.out.println(Thread.currentThread().getName() + ": " + num); num++; oddCondition.signal(); } else { evenCondition.await(); } } catch (InterruptedException e) { Thread.currentThread().interrupt(); } finally { lock.unlock(); } } } } public class Main { public static void main(String[] args) throws InterruptedException { Scanner scanner = new Scanner(System.in); int n = scanner.nextInt(); // 传入参数n，用于后续构造方法接收参数max，并把参数的值赋值给成员变量this.max(private final int max) PrintOddEven printOddEven = new PrintOddEven(n); // ""里存放的是线程名称，会被子函数的Thread.currentThread().getName()获取到 Thread oddThread = new Thread(() -> printOddEven.printOdd(), "OddThread"); Thread evenThread = new Thread(() -> printOddEven.printEven(), "EvenThread"); oddThread.start(); evenThread.start(); oddThread.join(); evenThread.join(); scanner.close(); } }二、方法二：Synchronized + wait/notify
import java.util.Scanner; class PrintOddEven { private int num = 1; private final int max; private final Object lock = new Object(); public PrintOddEven(int max) { this.max = max; } public void printOdd() { synchronized (lock) { while (num <= max) { if (num % 2 != 0) { System.out.println(Thread.currentThread().getName() + ": " + num); num++; lock.notify(); } else { try { lock.wait(); } catch (InterruptedException e) { Thread.currentThread().interrupt(); } } } } } public void printEven() { synchronized (lock) { while (num <= max) { if (num % 2 == 0) { System.out.println(Thread.currentThread().getName() + ": " + num); num++; lock.notify(); } else { try { lock.wait(); } catch (InterruptedException e) { Thread.currentThread().interrupt(); } } } } } } public class Main { public static void main(String[] args) throws InterruptedException { Scanner scanner = new Scanner(System.in); // 读取最大值 int n = scanner.nextInt(); PrintOddEven printOddEven = new PrintOddEven(n); // 创建两个线程 Thread oddThread = new Thread(() -> printOddEven.printOdd(), "OddThread"); Thread evenThread = new Thread(() -> printOddEven.printEven(), "EvenThread"); // 启动线程 oddThread.start(); evenThread.start(); // 等待线程结束 oddThread.join(); evenThread.join(); scanner.close(); } }三、方法三：使用信号量 Semaphore（最简洁）
import java.util.Scanner; import java.util.concurrent.Semaphore; class PrintOddEven { private int num = 1; private final int max; private final Semaphore oddSemaphore = new Semaphore(1); private final Semaphore evenSemaphore = new Semaphore(0); public PrintOddEven(int max) { this.max = max; } public void printOdd() { while (num <= max) { try { oddSemaphore.acquire(); if (num <= max) { System.out.println(Thread.currentThread().getName() + ": " + num); num++; } evenSemaphore.release(); } catch (InterruptedException e) { Thread.currentThread().interrupt(); } } } public void printEven() { while (num <= max) { try { evenSemaphore.acquire(); if (num <= max) { System.out.println(Thread.currentThread().getName() + ": " + num); num++; } oddSemaphore.release(); } catch (InterruptedException e) { Thread.currentThread().interrupt(); } } } } public class Main { public static void main(String[] args) throws InterruptedException { Scanner scanner = new Scanner(System.in); int n = scanner.nextInt(); PrintOddEven printOddEven = new PrintOddEven(n); Thread oddThread = new Thread(() -> printOddEven.printOdd(), "OddThread"); Thread evenThread = new Thread(() -> printOddEven.printEven(), "EvenThread"); oddThread.start(); evenThread.start(); oddThread.join(); evenThread.join(); scanner.close(); } }