CompletableFuture.thenApply
时间: 2023-11-07 20:03:51 浏览: 50
CompletableFuture.thenApply是Java的一个方法,用于在CompletableFuture完成后应用一个函数。它接受一个Function作为参数,该函数将在CompletableFuture完成时被应用,并返回一个新的CompletableFuture,其结果是应用该函数后的结果。
下面是使用thenApply的示例代码:
```java
CompletableFuture<Integer> future = CompletableFuture.supplyAsync(() -> 10);
CompletableFuture<String> result = future.thenApply(num -> "Result: " + num * 2);
System.out.println(result.get()); // 输出: Result: 20
```
在上面的示例中,我们首先创建了一个CompletableFuture对象,该对象会在后台线程中执行一个任务并返回结果。然后我们调用了thenApply方法,传入一个lambda表达式作为参数,该lambda表达式将结果乘以2并添加前缀字符串。最后,我们通过调用get方法来获取最终的结果。
相关问题
CompletableFuture.supplyAsync
CompletableFuture.supplyAsync is a method in Java's CompletableFuture class that allows you to create a CompletableFuture with a supplier function. This method is typically used when you want to asynchronously execute a task and obtain its result. The supplier function is responsible for providing the result value.
Here's an example of how to use CompletableFuture.supplyAsync:
```java
CompletableFuture<String> future = CompletableFuture.supplyAsync(() -> {
// Perform some task to generate a result
return "Hello, world!";
});
// You can then use the CompletableFuture to perform other actions, such as applying transformations or handling the result
future.thenApply(result -> {
// Manipulate the result
return result.toUpperCase();
}).thenAccept(result -> {
// Consume the manipulated result
System.out.println(result);
});
```
In this example, the supplyAsync method is used to asynchronously execute a task that returns the string "Hello, world!". The thenApply method is then used to transform the result to uppercase, and finally, the thenAccept method is used to consume and print the manipulated result.
I hope this answers your question! Let me know if you have any more.
CompletableFuture.allOf 异常处理
CompletableFuture.allOf方法用于组合多个CompletableFuture对象,并在所有任务完成后返回一个新的CompletableFuture对象。然而,CompletableFuture.allOf方法本身并不处理异常,它只是等待所有任务完成。
要处理CompletableFuture.allOf方法中的异常,可以使用whenComplete方法。whenComplete方法可以在任务完成时触发回调函数,无论是正常完成还是发生异常。通过在whenComplete方法中处理异常,我们可以确保异常得到正确的传播和处理。
下面是一个示例代码,演示了如何使用CompletableFuture.allOf方法和whenComplete方法来处理异常:
```java
CompletableFuture<Integer> future1 = CompletableFuture.supplyAsync(() -> {
// 任务1
throw new RuntimeException("Oops!");
});
CompletableFuture<Integer> future2 = CompletableFuture.supplyAsync(() -> {
// 任务2
return 42;
});
CompletableFuture<Void> allFutures = CompletableFuture.allOf(future1, future2);
CompletableFuture<String> result = allFutures.thenApply(v -> {
// 所有任务完成后的处理
if (future1.isCompletedExceptionally()) {
// 处理任务1的异常
Throwable ex = future1.getCompletionException();
System.out.println("Error occurred in future1: " + ex);
return "Error";
} else if (future2.isCompletedExceptionally()) {
// 处理任务2的异常
Throwable ex = future2.getCompletionException();
System.out.println("Error occurred in future2: " + ex);
return "Error";
} else {
// 所有任务正常完成
return "Success";
}
});
result.join(); // 等待结果
```
在上面的代码中,我们使用CompletableFuture.allOf方法组合了future1和future2,并使用thenApply方法处理所有任务完成后的结果。在thenApply方法中,我们通过判断每个任务是否发生异常来处理异常情况,并返回相应的结果。
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