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BAEL-1078 How to iterate over a stream with indices (#2544) 

* Add the example with EntryStream

* Add the example with EntryStream

* Add vavr

* Implement the method getOddIndexedStringsVersionTwo

* Implement the method givenArray_whenGetIndexedStrings_thenReturnListOfOddStringsVersionTwo

* BAEL-1078 Code formatting

* Extract tuples using map

* Fix merge conflicts
This commit is contained in:
Fatos Morina 2017-09-02 10:42:24 +02:00 committed by Eugen
parent d635e9a245
commit 94d02ed1f6
1 changed files with 24 additions and 34 deletions
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58
core-java/src/main/java/com/baeldung/stream/StreamIndices.java
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@ -1,6 +1,5 @@
package com.baeldung.stream; package com.baeldung.stream;
import java.util.ArrayList;
import java.util.List; import java.util.List;
import java.util.stream.Collectors; import java.util.stream.Collectors;
import java.util.stream.IntStream; import java.util.stream.IntStream;
@ -8,65 +7,56 @@ import java.util.stream.IntStream;
import com.codepoetics.protonpack.Indexed; import com.codepoetics.protonpack.Indexed;
import com.codepoetics.protonpack.StreamUtils; import com.codepoetics.protonpack.StreamUtils;
import io.vavr.Tuple2;
import io.vavr.collection.Stream; import io.vavr.collection.Stream;
import one.util.streamex.EntryStream; import one.util.streamex.EntryStream;
public class StreamIndices { public class StreamIndices {
public static List<String> getEvenIndexedStrings(String[] names) { public static List<String> getEvenIndexedStrings(String[] names) {
List<String> evenIndexedNames = IntStream List<String> evenIndexedNames = IntStream.range(0, names.length)
.range(0, names.length) .filter(i -> i % 2 == 0)
.filter(i -> i % 2 == 0) .mapToObj(i -> names[i])
.mapToObj(i -> names[i]) .collect(Collectors.toList());
.collect(Collectors.toList());
return evenIndexedNames; return evenIndexedNames;
} }
public List<String> getEvenIndexedStringsVersionTwo(List<String> names) { public List<String> getEvenIndexedStringsVersionTwo(List<String> names) {
List<String> evenIndexedNames = EntryStream List<String> evenIndexedNames = EntryStream.of(names)
.of(names) .filterKeyValue((index, name) -> index % 2 == 0)
.filterKeyValue((index, name) -> index % 2 == 0) .values()
.values() .toList();
.toList();
return evenIndexedNames; return evenIndexedNames;
} }
public static List<Indexed<String>> getEvenIndexedStrings(List<String> names) { public static List<Indexed<String>> getEvenIndexedStrings(List<String> names) {
List<Indexed<String>> list = StreamUtils List<Indexed<String>> list = StreamUtils.zipWithIndex(names.stream())
.zipWithIndex(names.stream()) .filter(i -> i.getIndex() % 2 == 0)
.filter(i -> i.getIndex() % 2 == 0) .collect(Collectors.toList());
.collect(Collectors.toList());
return list; return list;
} }
public static List<Indexed<String>> getOddIndexedStrings(List<String> names) { public static List<Indexed<String>> getOddIndexedStrings(List<String> names) {
List<Indexed<String>> list = StreamUtils List<Indexed<String>> list = StreamUtils.zipWithIndex(names.stream())
.zipWithIndex(names.stream()) .filter(i -> i.getIndex() % 2 == 1)
.filter(i -> i.getIndex() % 2 == 1) .collect(Collectors.toList());
.collect(Collectors.toList());
return list; return list;
} }
public static List<String> getOddIndexedStrings(String[] names) { public static List<String> getOddIndexedStrings(String[] names) {
List<String> oddIndexedNames = IntStream List<String> oddIndexedNames = IntStream.range(0, names.length)
.range(0, names.length) .filter(i -> i % 2 == 1)
.filter(i -> i % 2 == 1) .mapToObj(i -> names[i])
.mapToObj(i -> names[i]) .collect(Collectors.toList());
.collect(Collectors.toList());
return oddIndexedNames; return oddIndexedNames;
} }
public static List<String> getOddIndexedStringsVersionTwo(String[] names) { public static List<String> getOddIndexedStringsVersionTwo(String[] names) {
List<Tuple2<String, Integer>> tuples = Stream List<String> oddIndexedNames = Stream.of(names)
.of(names) .zipWithIndex()
.zipWithIndex() .filter(tuple -> tuple._2 % 2 == 1)
.filter(tuple -> tuple._2 % 2 == 1) .map(tuple -> tuple._1)
.toJavaList(); .toJavaList();
List<String> oddIndexedNames = new ArrayList<String>();
tuples.forEach(tuple -> {
oddIndexedNames.add(tuple._1);
});
return oddIndexedNames; return oddIndexedNames;
} }
} }