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Added example for Supplier lazy generation, corrected the reduce example (#638)

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Sergey Petunin 2016-08-25 14:30:40 +06:00 committed by Grzegorz Piwowarek
parent 9ae8b346d9
commit 743f6c8806
1 changed files with 23 additions and 3 deletions
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core-java-8/src/test/java/com/baeldung/functionalinterface/FunctionalInterfaceTest.java
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@ -1,15 +1,18 @@
package com.baeldung.functionalinterface; package com.baeldung.functionalinterface;
import org.junit.Test;
import java.util.Arrays; import java.util.Arrays;
import java.util.HashMap; import java.util.HashMap;
import java.util.List; import java.util.List;
import java.util.Map; import java.util.Map;
import java.util.concurrent.TimeUnit;
import java.util.function.Function; import java.util.function.Function;
import java.util.function.Supplier;
import java.util.stream.Collectors; import java.util.stream.Collectors;
import java.util.stream.Stream; import java.util.stream.Stream;
import com.google.common.util.concurrent.Uninterruptibles;
import org.junit.Test;
import static org.junit.Assert.*; import static org.junit.Assert.*;
public class FunctionalInterfaceTest { public class FunctionalInterfaceTest {
@ -157,7 +160,7 @@ public class FunctionalInterfaceTest {
List<Integer> values = Arrays.asList(3, 5, 8, 9, 12); List<Integer> values = Arrays.asList(3, 5, 8, 9, 12);
int sum = values.stream() int sum = values.stream()
.reduce(0, (acc, value) -> acc + value); .reduce(0, (i1, i2) -> i1 + i2);
assertEquals(37, sum); assertEquals(37, sum);
@ -175,5 +178,22 @@ public class FunctionalInterfaceTest {
} }
public double squareLazy(Supplier<Double> lazyValue) {
return Math.pow(lazyValue.get(), 2);
}
@Test
public void whenUsingSupplierToGenerateValue_thenValueIsGeneratedLazily() {
Supplier<Double> lazyValue = () -> {
Uninterruptibles.sleepUninterruptibly(1000, TimeUnit.MILLISECONDS);
return 9d;
};
double valueSquared = squareLazy(lazyValue);
assertEquals(81d, valueSquared, 0);
}
} }