70 lines
1.7 KiB
Java
70 lines
1.7 KiB
Java
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// concurrent/CompletableExceptions.java
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// (c)2016 MindView LLC: see Copyright.txt
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// We make no guarantees that this code is fit for any purpose.
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// Visit http://OnJava8.com for more book information.
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import java.util.concurrent.*;
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import onjava.Nap;
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public class CompletableExceptions {
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static CompletableFuture<Breakable>
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test(String id, int failcount) {
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return
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CompletableFuture.completedFuture(
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new Breakable(id, failcount))
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.thenApply(Breakable::work)
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.thenApply(Breakable::work)
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.thenApply(Breakable::work)
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.thenApply(Breakable::work);
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}
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public static void main(String[] args) {
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// Exceptions don't appear ...
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test("A", 1);
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test("B", 2);
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test("C", 3);
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test("D", 4);
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test("E", 5);
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// ... until you try to fetch the value:
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try {
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test("F", 2).get(); // or join()
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} catch(Exception e) {
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System.out.println(e.getMessage());
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}
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// Test for exceptions:
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System.out.println(
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test("G", 2).isCompletedExceptionally());
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// Counts as "done":
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System.out.println(test("H", 2).isDone());
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// Force an exception:
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CompletableFuture<Integer> cfi =
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new CompletableFuture<>();
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System.out.println("done? " + cfi.isDone());
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cfi.completeExceptionally(
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new RuntimeException("forced"));
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try {
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cfi.get();
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} catch(Exception e) {
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System.out.println(e.getMessage());
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}
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}
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}
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/* Output:
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Breakable_B [1]
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Breakable_C [2]
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Breakable_C [1]
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Breakable_D [3]
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Breakable_D [2]
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Breakable_D [1]
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Breakable_E [4]
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Breakable_E [3]
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Breakable_E [2]
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Breakable_E [1]
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Breakable_F [1]
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java.lang.RuntimeException: Breakable_F failed
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Breakable_G [1]
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true
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Breakable_H [1]
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true
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done? false
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java.lang.RuntimeException: forced
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*/
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