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Stream Utils for handling common collection processing use cases
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import java.util.*; | |
import java.util.function.Function; | |
import java.util.function.Predicate; | |
import java.util.stream.Collectors; | |
public class StreamUtils { | |
public static <S, D> List<D> mapToList(Collection<S> sourceList, Function<S, D> mapFunction){ | |
if (sourceList == null || sourceList.isEmpty()) return Collections.emptyList(); | |
return sourceList | |
.stream() | |
.map(mapFunction) | |
.collect(Collectors.toList()); | |
} | |
public static <S, D> Set<D> mapToSet(Collection<S> sourceList, Function<S, D> mapFunction){ | |
if (sourceList == null || sourceList.isEmpty()) return Collections.emptySet(); | |
return sourceList | |
.stream() | |
.map(mapFunction) | |
.collect(Collectors.toSet()); | |
} | |
public static <S, D> List<D> mapToList(S[] sourceList, Function<S, D> mapFunction){ | |
if (sourceList == null) return Collections.emptyList(); | |
return Arrays.asList(sourceList) | |
.stream() | |
.map(mapFunction) | |
.collect(Collectors.toList()); | |
} | |
public static <S> Set<S> filterToSet(Collection<S> sourceList, Predicate<S> condition){ | |
if (sourceList == null || sourceList.isEmpty()) return Collections.emptySet(); | |
return sourceList | |
.stream() | |
.filter(condition) | |
.collect(Collectors.toSet()); | |
} | |
// return null if not found or empty | |
public static <S> S first(Collection<S> sourceList){ | |
if (sourceList == null || sourceList.isEmpty()) return null; | |
return sourceList | |
.stream() | |
.findFirst() | |
.orElse(null); | |
} | |
// return null if not found or empty | |
public static <S> S first(S[] sourceList){ | |
if (sourceList == null || sourceList.length == 0) return null; | |
return Arrays.stream(sourceList) | |
.findFirst() | |
.orElse(null); | |
} | |
// return null if not found or empty | |
public static <S> S firstMatch(Collection<S> sourceList, Predicate<S> condition){ | |
if (sourceList == null || sourceList.isEmpty()) return null; | |
return sourceList | |
.stream() | |
.filter(condition) | |
.findFirst() | |
.orElse(null); | |
} | |
// return null if not found or empty | |
public static <S> S firstMatch(S[] sourceList, Predicate<S> condition){ | |
if (sourceList == null || sourceList.length == 0) return null; | |
return Arrays.stream(sourceList) | |
.filter(condition) | |
.findFirst() | |
.orElse(null); | |
} | |
public static <S> List<S> filterToList(Collection<S> sourceList, Predicate<S> condition) { | |
if (sourceList == null || sourceList.isEmpty()) return Collections.emptyList(); | |
return sourceList | |
.stream() | |
.filter(condition) | |
.collect(Collectors.toList()); | |
} | |
public static <I, O> Map<I, O> toIdMap(Collection<O> sourceList, Function<O, I> idFunction) { | |
Map<I, O> map = new HashMap<>(); | |
if (sourceList == null || sourceList.isEmpty()) return map; | |
sourceList.forEach(element -> map.put(idFunction.apply(element), element)); | |
return map; | |
} | |
public static <I, O> Set<O> getMapValueWithIds(Map<I, O> map, List<I> ids) { | |
if (map == null || map.isEmpty()) return new HashSet<>(); | |
return ids.stream().map(i -> map.getOrDefault(i, null)).filter(Objects::nonNull).collect(Collectors.toSet()); | |
} | |
} |
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