Java多线程并发问题：打印顺序

原创我不是女神ヾ 2024-11-07 12:00 35阅读 0赞

Java多线程并发问题中，打印顺序是一个常见的问题，它涉及到线程的启动、执行和同步。以下是一些常见的多线程打印顺序问题及其解决方案：

###1.顺序打印数字**问题描述**：有三个线程，分别打印数字1-10，要求每个线程打印的数字是连续的。

**解决方案**：
- 使用`synchronized`关键字同步代码块，确保一次只有一个线程可以执行打印操作。
- 使用`wait()`和`notify()`方法控制线程的执行顺序。

```javapublic class PrintNumber {
 private int number =1;
 private final int max =10;
 private final Object lock = new Object();

public void printNumberA() {
 for (; number <= max; number++) {
 synchronized (lock) {
if (number %3 !=0) {
 try {
lock.wait();
} catch (InterruptedException e) {
e.printStackTrace();
 }
} else {
 System.out.println(Thread.currentThread().getName() + "打印：" + number);
lock.notifyAll();
 }
 }
 }
 }

public void printNumberB() {
 for (; number <= max; number++) {
 synchronized (lock) {
if (number %3 !=1) {
 try {
lock.wait();
} catch (InterruptedException e) {
e.printStackTrace();
 }
} else {
 System.out.println(Thread.currentThread().getName() + "打印：" + number);
lock.notifyAll();
 }
 }
 }
 }

public void printNumberC() {
 for (; number <= max; number++) {
 synchronized (lock) {
if (number %3 !=2) {
 try {
lock.wait();
} catch (InterruptedException e) {
e.printStackTrace();
 }
} else {
 System.out.println(Thread.currentThread().getName() + "打印：" + number);
lock.notifyAll();
 }
 }
 }
 }

public static void main(String[] args) {
 PrintNumber printNumber = new PrintNumber();
Thread threadA = new Thread(printNumber::printNumberA, "线程A");
Thread threadB = new Thread(printNumber::printNumberB, "线程B");
Thread threadC = new Thread(printNumber::printNumberC, "线程C");

threadA.start();
 threadB.start();
 threadC.start();
 }
}
```###2.交替打印奇偶数**问题描述**：两个线程交替打印奇数和偶数。

**解决方案**：
- 使用`synchronized`关键字同步代码块。
- 使用`wait()`和`notify()`方法控制线程的执行顺序。

```javapublic class PrintOddEven {
 private boolean isOdd = true;

public synchronized void printOdd() {
 while (!isOdd) {
 try {
 wait();
} catch (InterruptedException e) {
e.printStackTrace();
 }
 }
 for (int i =1; i <=10; i +=2) {
 System.out.println(Thread.currentThread().getName() + "打印奇数：" + i);
isOdd = false;
 notify();
 }
 }

public synchronized void printEven() {
 while (isOdd) {
 try {
 wait();
} catch (InterruptedException e) {
e.printStackTrace();
 }
 }
 for (int i =2; i <=10; i +=2) {
 System.out.println(Thread.currentThread().getName() + "打印偶数：" + i);
isOdd = true;
 notify();
 }
 }

public static void main(String[] args) {
 PrintOddEven printOddEven = new PrintOddEven();
Thread threadOdd = new Thread(printOddEven::printOdd, "打印奇数");
Thread threadEven = new Thread(printOddEven::printEven, "打印偶数");

threadOdd.start();
 threadEven.start();
 }
}
```###3.交替打印字母和数字**问题描述**：两个线程交替打印字母和数字。

**解决方案**：
- 使用`synchronized`关键字同步代码块。
- 使用`wait()`和`notify()`方法控制线程的执行顺序。

```javapublic class PrintLetterNumber {
 private boolean isLetter = true;

public synchronized void printLetter() {
 while (!isLetter) {
 try {
 wait();
} catch (InterruptedException e) {
e.printStackTrace();
 }
 }
 for (char c = 'A'; c <= 'Z'; c++) {
 System.out.println(Thread.currentThread().getName() + "打印字母：" + c);
isLetter = false;
 notify();
 }
 }

public synchronized void printNumber() {
 while (isLetter) {