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Example 3.3 Advanced error handling
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‎tests/java/itrx/chapter3/error/ResumeTest.java‎

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package itrx.chapter3.error;
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import static org.junit.Assert.assertEquals;
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import static org.junit.Assert.assertThat;
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import java.util.Arrays;
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import org.junit.Test;
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import rx.Observable;
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import rx.Subscriber;
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import rx.observers.TestSubscriber;
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public class ResumeTest {
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private static class PrintSubscriber extends Subscriber<Object>{
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private final String name;
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public PrintSubscriber(String name) {
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this.name = name;
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}
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@Override
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public void onCompleted() {
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System.out.println(name + ": Completed");
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}
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@Override
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public void onError(Throwable e) {
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System.out.println(name + ": Error: " + e);
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}
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@Override
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public void onNext(Object v) {
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System.out.println(name + ": " + v);
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}
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}
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public void exampleOnErrorReturn() {
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Observable<String> values = Observable.create(o -> {
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o.onNext("Rx");
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o.onNext("is");
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o.onError(new Exception("adjective unknown"));
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});
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values
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.onErrorReturn(e -> "Error: " + e.getMessage())
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.subscribe(v -> System.out.println(v));
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// Rx
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// is
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// Error: adjective unknown
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}
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public void exampleOnErrorResumeNext() {
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Observable<Integer> values = Observable.create(o -> {
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o.onNext(1);
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o.onNext(2);
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o.onError(new Exception("Oops"));
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});
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values
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.onErrorResumeNext(Observable.just(Integer.MAX_VALUE))
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.subscribe(new PrintSubscriber("with onError: "));
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// with onError: 1
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// with onError: 2
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// with onError: 2147483647
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// with onError: Completed
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}
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public void exampleOnErrorResumeNextRethrow() {
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Observable<Integer> values = Observable.create(o -> {
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o.onNext(1);
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o.onNext(2);
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o.onError(new Exception("Oops"));
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});
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values
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.onErrorResumeNext(e -> Observable.error(new UnsupportedOperationException(e)))
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.subscribe(new PrintSubscriber("with onError: "));
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}
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public void exampleOnExceptionResumeNext() {
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Observable<String> values = Observable.create(o -> {
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o.onNext("Rx");
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o.onNext("is");
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o.onError(new Exception()); // this will be caught
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});
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values
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.onExceptionResumeNext(Observable.just("hard"))
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.subscribe(v -> System.out.println(v));
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}
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@SuppressWarnings("serial")
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public void exampleOnExceptionResumeNextNoException() {
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Observable<String> values = Observable.create(o -> {
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o.onNext("Rx");
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o.onNext("is");
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o.onError(new Throwable() {}); // this won't be caught
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});
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values
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.onExceptionResumeNext(Observable.just("hard"))
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.subscribe(v -> System.out.println(v));
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}
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//
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// Tests
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//
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@Test
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public void testOnErrorReturn() {
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TestSubscriber<String> tester = new TestSubscriber<>();
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Observable<String> values = Observable.create(o -> {
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o.onNext("Rx");
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o.onNext("is");
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o.onError(new Exception("adjective unknown"));
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});
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values
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.onErrorReturn(e -> "Error: " + e.getMessage())
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.subscribe(tester);
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tester.assertReceivedOnNext(Arrays.asList(
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"Rx",
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"is",
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"Error: adjective unknown"));
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tester.assertTerminalEvent();
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tester.assertNoErrors();
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}
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@Test
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public void testerOnErrorResumeNext() {
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TestSubscriber<Integer> tester = new TestSubscriber<>();
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Observable<Integer> values = Observable.create(o -> {
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o.onNext(1);
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o.onNext(2);
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o.onError(new Exception("Oops"));
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});
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values
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.onErrorResumeNext(Observable.just(Integer.MAX_VALUE))
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.subscribe(tester);
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tester.assertReceivedOnNext(Arrays.asList(1,2,Integer.MAX_VALUE));
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tester.assertTerminalEvent();
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tester.assertNoErrors();
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}
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@Test
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public void testOnErrorResumeNextRethrow() {
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TestSubscriber<Integer> tester = new TestSubscriber<>();
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Observable<Integer> values = Observable.create(o -> {
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o.onNext(1);
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o.onNext(2);
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o.onError(new Exception("Oops"));
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});
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values
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.onErrorResumeNext(e -> Observable.error(new UnsupportedOperationException(e)))
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.subscribe(tester);
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tester.assertReceivedOnNext(Arrays.asList(1,2));
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tester.assertTerminalEvent();
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assertThat(tester.getOnErrorEvents().get(0),
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org.hamcrest.CoreMatchers.instanceOf(UnsupportedOperationException.class));
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}
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@Test
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public void testOnExceptionResumeNext() {
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TestSubscriber<String> tester = new TestSubscriber<>();
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Observable<String> values = Observable.create(o -> {
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o.onNext("Rx");
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o.onNext("is");
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o.onError(new Exception()); // this will be caught
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});
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values
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.onExceptionResumeNext(Observable.just("hard"))
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.subscribe(tester);
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tester.assertReceivedOnNext(Arrays.asList("Rx","is","hard"));
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tester.assertTerminalEvent();
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tester.assertNoErrors();
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}
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@SuppressWarnings("serial")
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@Test
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public void testOnExceptionResumeNextNoException() {
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TestSubscriber<String> tester = new TestSubscriber<>();
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Observable<String> values = Observable.create(o -> {
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o.onNext("Rx");
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o.onNext("is");
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o.onError(new Throwable() {}); // this won't be caught
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});
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values
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.onExceptionResumeNext(Observable.just("hard"))
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.subscribe(tester);
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tester.assertTerminalEvent();
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assertEquals(tester.getOnErrorEvents().size(), 1);
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}
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}

‎tests/java/itrx/chapter3/error/RetryTest.java‎

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package itrx.chapter3.error;
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import static org.junit.Assert.*;
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import java.util.Random;
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import org.junit.Test;
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import rx.Observable;
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import rx.observers.TestSubscriber;
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public class RetryTest {
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public void exampleRetry() {
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Random random = new Random();
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Observable<Integer> values = Observable.create(o -> {
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o.onNext(random.nextInt() % 20);
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o.onNext(random.nextInt() % 20);
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o.onError(new Exception());
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});
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values
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.retry(1)
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.subscribe(v -> System.out.println(v));
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// 0
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// 13
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// 9
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// 15
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// java.lang.Exception
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}
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//
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// Test
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//
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@Test
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public void testRetry() {
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TestSubscriber<Integer> tester = new TestSubscriber<>();
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Random random = new Random();
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Observable<Integer> values = Observable.create(o -> {
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o.onNext(random.nextInt() % 20);
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o.onNext(random.nextInt() % 20);
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o.onError(new Exception());
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});
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values
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.retry(1)
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.subscribe(tester);
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assertEquals(tester.getOnNextEvents().size(), 4);
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tester.assertTerminalEvent();
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assertEquals(tester.getOnErrorEvents().size(), 1);
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}
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}

‎tests/java/itrx/chapter3/error/UsingTest.java‎

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package itrx.chapter3.error;
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import static org.junit.Assert.assertEquals;
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import java.util.Arrays;
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import org.junit.Test;
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import rx.Observable;
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import rx.observers.TestSubscriber;
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public class UsingTest {
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public void exampleUsing() {
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Observable<Character> values = Observable.using(
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() -> {
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String resource = "MyResource";
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System.out.println("Leased: " + resource);
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return resource;
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},
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(resource) -> {
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return Observable.create(o -> {
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for (Character c : resource.toCharArray())
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o.onNext(c);
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o.onCompleted();
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});
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},
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(resource) -> System.out.println("Disposed: " + resource));
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values
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.subscribe(
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v -> System.out.println(v),
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e -> System.out.println(e));
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// Leased: MyResource
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// M
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// y
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// R
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// e
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// s
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// o
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// u
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// r
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// c
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// e
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// Disposed: MyResource
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}
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//
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// Test
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//
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@Test
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public void testUsing() {
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TestSubscriber<Character> tester = new TestSubscriber<>();
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String[] leaseRelease = {"", ""};
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Observable<Character> values = Observable.using(
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() -> {
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String resource = "MyResource";
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leaseRelease[0] = resource;
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return resource;
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},
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(resource) -> {
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return Observable.create(o -> {
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for (Character c : resource.toCharArray())
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o.onNext(c);
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o.onCompleted();
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});
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},
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(resource) -> leaseRelease[1] = resource);
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values
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.subscribe(tester);
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assertEquals(leaseRelease[0], leaseRelease[1]);
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tester.assertReceivedOnNext(Arrays.asList('M','y','R','e','s','o','u','r','c','e'));
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tester.assertTerminalEvent();
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tester.assertNoErrors();
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}
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}

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