public synchronized void method() { ... } // 實(shí)例方法鎖（this）
public static synchronized void method() { ... } // 類方法鎖（Class 對(duì)象）
// 鎖實(shí)例對(duì)象
synchronized (lockObject) {
    // 同步代碼塊
}

ReentrantLock lock = new ReentrantLock();
lock.lock();
try {
    // 同步代碼
} finally {
    lock.unlock();
}

Semaphore semaphore = new Semaphore(3); // 初始許可數(shù)為3
semaphore.acquire(); // 獲取許可
try {
    // 同步代碼
} finally {
    semaphore.release(); // 釋放許可
}

public class LatchDemo {
    public static void main(String[] args) throws InterruptedException {
        int threadCount = 3;
        CountDownLatch latch = new CountDownLatch(threadCount);
        for (int i = 1; i <= threadCount; i++) {
            new Thread(() -> {
                System.out.println(Thread.currentThread().getName() + " 初始化完成");
                latch.countDown(); // 子線程完成，計(jì)數(shù)器減 1
            }, "線程-" + i).start();
        }
        latch.await(); // 主線程等待所有子線程完成
        System.out.println("所有子線程完成，主線程繼續(xù)執(zhí)行");
    }
}

import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class CyclicBarrierExample {
    // 總和變量（線程安全）
    private static int sum = 0;
    // 線程池
    private static final ExecutorService executor = Executors.newFixedThreadPool(5);
    public static void main(String[] args) {
        // 定義需要等待的線程數(shù)量（5個(gè)）
        CyclicBarrier cyclicBarrier = new CyclicBarrier(5, () -> {
            // 所有線程到達(dá)屏障后執(zhí)行的回調(diào)（匯總結(jié)果）
            System.out.println("所有線程已完成計(jì)算，總和為: " + sum);
        });
        // 啟動(dòng)5個(gè)線程
        for (int i = 0; i < 5; i++) {
            executor.execute(() -> {
                try {
                    // 模擬線程計(jì)算
                    int value = (int) (Math.random() * 100);
                    System.out.println(Thread.currentThread().getName() + " 計(jì)算值: " + value);
                    // 將計(jì)算結(jié)果累加到總和中
                    sum += value;
                    // 調(diào)用await()等待其他線程到達(dá)屏障
                    cyclicBarrier.await();
                } catch (InterruptedException | BrokenBarrierException e) {
                    e.printStackTrace();
                }
            });
        }
        // 關(guān)閉線程池
        executor.shutdown();
    }
}

Phaser phaser = new Phaser(1); // 初始參與線程
phaser.bulkRegister(3);        // 動(dòng)態(tài)注冊(cè)3個(gè)工作線程
for (int i = 0; i < 3; i++) {
    new Thread(() -> {
        for (int phase = 0; phase < 2; phase++) {
            phaser.arriveAndAwaitAdvance(); // 階段1：等待所有線程完成階段1
            // 執(zhí)行階段2任務(wù)
        }
        phaser.arriveAndDeregister(); // 完成并注銷
    }).start();
}
// 主線程等待所有線程完成
phaser.arriveAndAwaitAdvance();

Error updating database. Cause: ERR-CODE: [TDDL-4614][ERR EXECUTE ON MYSQL]
Deadlock found when trying to get lock;
The error occurred while setting parameters### SQL:
update test_table set updated=now(),type_state = ? where test_num = 123

CompletableFuture<Void> future = CompletableFuture.runAsync(() -> {
    System.out.println("無(wú)返回值任務(wù)執(zhí)行中");
});

CompletableFuture<String> future = CompletableFuture.supplyAsync(() -> {
    return "異步任務(wù)結(jié)果";
});
System.out.println(future.get()); // 輸出: 異步任務(wù)結(jié)果

ExecutorService executor = Executors.newFixedThreadPool(2);
CompletableFuture<String> future = CompletableFuture.supplyAsync(() -> {
    return "自定義線程池任務(wù)";
}, executor);

CompletableFuture<String> future = CompletableFuture.supplyAsync(() -> "Hello")
    .thenApplyAsync(result -> result + " World");// 運(yùn)行結(jié)果 Hello World

CompletableFuture<Void> future = CompletableFuture.supplyAsync(() -> {
            return "Hello";
        }).thenRunAsync(() -> {
            System.out.println("after Hello World");
        });

CompletableFuture<String> future = CompletableFuture.supplyAsync(() -> "Hello")
.thenCompose(result -> CompletableFuture.supplyAsync(() -> result + " World"));
System.out.println(future.get()); // 輸出: Hello World

CompletableFuture<String> future1 = CompletableFuture.supplyAsync(() -> "Hello");
CompletableFuture<String> future2 = CompletableFuture.supplyAsync(() -> "World");
future1.thenCombine(future2, (result1, result2) -> result1 + " " + result2)
       .thenAccept(System.out::println); // 輸出: Hello World

CompletableFuture<Void> allFutures = CompletableFuture.allOf(
    CompletableFuture.runAsync(() -> System.out.println("Task 1")),
    CompletableFuture.runAsync(() -> System.out.println("Task 2"))
);
allFutures.get(); // 等待所有任務(wù)完成

CompletableFuture<Object> anyFuture = CompletableFuture.anyOf(
    CompletableFuture.supplyAsync(() -> "Task 1"),
    CompletableFuture.supplyAsync(() -> "Task 2")
);
System.out.println(anyFuture.get()); // 輸出: Task 1 或 Task 2（取決于哪個(gè)先完成）

CompletableFuture<String> future = CompletableFuture.supplyAsync(() -> {
    if (Math.random() > 0.5) throw new RuntimeException("失敗");
    return "成功";
}).exceptionally(ex -> {
    System.out.println("異常處理: " + ex.getMessage());
    return "默認(rèn)值";
});
System.out.println(future.get());

CompletableFuture<String> future = CompletableFuture.supplyAsync(() -> {
    if (Math.random() > 0.5) throw new RuntimeException("失敗");
    return "成功";
}).handle((result, ex) -> {
    if (ex != null) {
        System.out.println("異常處理: " + ex.getMessage());
        return "默認(rèn)值";
    }
    return result;
});

CompletableFuture<String> future = CompletableFuture.supplyAsync(() -> {
    if (Math.random() > 0.5) throw new RuntimeException("失敗");
    return "成功";
}).whenComplete((result, ex) -> {
    if (ex != null) System.out.println("任務(wù)失敗");
    else System.out.println("任務(wù)成功: " + result);
});