[BAEL-2930] - array to stream conversion (#6931)
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package com.baeldung.array.conversions;
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import java.util.Arrays;
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import java.util.function.IntFunction;
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import java.util.stream.IntStream;
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import java.util.stream.Stream;
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public class StreamArrayConversion {
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public static String[] stringStreamToStringArrayUsingFunctionalInterface(Stream<String> stringStream) {
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IntFunction<String[]> intFunction = new IntFunction<String[]>() {
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@Override
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public String[] apply(int value) {
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return new String[value];
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}
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};
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return stringStream.toArray(intFunction);
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}
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public static String[] stringStreamToStringArrayUsingMethodReference(Stream<String> stringStream) {
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return stringStream.toArray(String[]::new);
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}
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public static String[] stringStreamToStringArrayUsingLambda(Stream<String> stringStream) {
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return stringStream.toArray(value -> new String[value]);
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}
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public static Integer[] integerStreamToIntegerArray(Stream<Integer> integerStream) {
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return integerStream.toArray(Integer[]::new);
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}
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public static int[] intStreamToPrimitiveIntArray(Stream<Integer> integerStream) {
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return integerStream.mapToInt(i -> i).toArray();
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}
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public static Stream<String> stringArrayToStreamUsingArraysStream(String[] stringArray) {
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return Arrays.stream(stringArray);
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}
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public static Stream<String> stringArrayToStreamUsingStreamOf(String[] stringArray) {
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return Stream.of(stringArray);
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}
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public static IntStream primitiveIntArrayToStreamUsingArraysStream(int[] intArray) {
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return Arrays.stream(intArray);
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}
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public static Stream<int[]> primitiveIntArrayToStreamUsingStreamOf(int[] intArray) {
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return Stream.of(intArray);
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}
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}
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package com.baeldung.array.conversions;
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import static com.baeldung.array.conversions.StreamArrayConversion.intStreamToPrimitiveIntArray;
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import static com.baeldung.array.conversions.StreamArrayConversion.integerStreamToIntegerArray;
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import static com.baeldung.array.conversions.StreamArrayConversion.stringStreamToStringArrayUsingFunctionalInterface;
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import static com.baeldung.array.conversions.StreamArrayConversion.stringStreamToStringArrayUsingLambda;
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import static com.baeldung.array.conversions.StreamArrayConversion.stringStreamToStringArrayUsingMethodReference;
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import static com.baeldung.array.conversions.StreamArrayConversion.stringArrayToStreamUsingArraysStream;
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import static com.baeldung.array.conversions.StreamArrayConversion.stringArrayToStreamUsingStreamOf;
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import static com.baeldung.array.conversions.StreamArrayConversion.primitiveIntArrayToStreamUsingArraysStream;
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import static com.baeldung.array.conversions.StreamArrayConversion.primitiveIntArrayToStreamUsingStreamOf;
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import static org.junit.Assert.assertArrayEquals;
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import static org.junit.Assert.assertFalse;
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import static org.junit.Assert.assertTrue;
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import com.google.common.collect.Iterators;
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import java.util.stream.IntStream;
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import java.util.stream.Stream;
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import org.junit.Test;
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public class StreamArrayConversionUnitTest {
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private String[] stringArray = new String[]{"baeldung", "convert", "to", "string", "array"};
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private Integer[] integerArray = new Integer[]{1, 2, 3, 4, 5, 6, 7};
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private int[] intPrimitiveArray = new int[]{1, 2, 3, 4, 5, 6, 7};
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@Test
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public void givenStringStream_thenConvertToStringArrayUsingFunctionalInterface() {
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Stream<String> stringStream = Stream.of("baeldung", "convert", "to", "string", "array");
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assertArrayEquals(stringArray, stringStreamToStringArrayUsingFunctionalInterface(stringStream));
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}
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@Test
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public void givenStringStream_thenConvertToStringArrayUsingMethodReference() {
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Stream<String> stringStream = Stream.of("baeldung", "convert", "to", "string", "array");
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assertArrayEquals(stringArray, stringStreamToStringArrayUsingMethodReference(stringStream));
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}
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@Test
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public void givenStringStream_thenConvertToStringArrayUsingLambda() {
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Stream<String> stringStream = Stream.of("baeldung", "convert", "to", "string", "array");
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assertArrayEquals(stringArray, stringStreamToStringArrayUsingLambda(stringStream));
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}
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@Test
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public void givenIntegerStream_thenConvertToIntegerArray() {
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Stream<Integer> integerStream = Stream.of(1, 2, 3, 4, 5, 6, 7);
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assertArrayEquals(integerArray, integerStreamToIntegerArray(integerStream));
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}
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@Test
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public void givenIntStream_thenConvertToIntegerArray() {
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Stream<Integer> integerStream = IntStream.rangeClosed(1, 7).boxed();
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assertArrayEquals(intPrimitiveArray, intStreamToPrimitiveIntArray(integerStream));
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}
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@Test
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public void givenStringArray_whenConvertedTwoWays_thenConvertedStreamsAreEqual() {
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assertTrue(Iterators
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.elementsEqual(stringArrayToStreamUsingArraysStream(stringArray).iterator(),
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stringArrayToStreamUsingStreamOf(stringArray).iterator()));
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}
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@Test
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public void givenPrimitiveArray_whenConvertedTwoWays_thenConvertedStreamsAreNotEqual() {
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assertFalse(Iterators.elementsEqual(
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primitiveIntArrayToStreamUsingArraysStream(intPrimitiveArray).iterator(),
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primitiveIntArrayToStreamUsingStreamOf(intPrimitiveArray).iterator()));
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}
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}
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