Package org.codehaus.groovy.runtime

Class StreamGroovyMethods

java.lang.Object
org.codehaus.groovy.runtime.StreamGroovyMethods
public class StreamGroovyMethods extends Object

  • Method Details

    • getAt

      public static <T> T getAt(Stream<T> self, int index)
      Returns element at index or null.

      This is a short-circuiting terminal operation. 

       import java.util.stream.Stream
 import static groovy.test.GroovyAssert.shouldFail

 Stream stream = ['foo','bar','baz'].stream()
 shouldFail(IllegalArgumentException) { stream[-1] }

 stream = ['foo','bar','baz'].stream()
 assert stream[0] == 'foo'

 stream = ['foo','bar','baz'].stream()
 assert stream[1] == 'bar'

 stream = ['foo','bar','baz'].stream()
 assert stream[2] == 'baz'

 stream = ['foo','bar','baz'].stream()
 assert stream[3] === null
      Throws:
      IllegalArgumentException - if index is negative
      Since:
      5.0.0

    • getAt

      public static <T> List<T> getAt(Stream<T> self, IntRange range)
      Returns element(s) in range or an empty list.

      This is a short-circuiting terminal operation. 

       import java.util.stream.Stream
 import static groovy.test.GroovyAssert.shouldFail

 Stream<String> stream = ['foo','bar','baz'].stream()
 shouldFail(IllegalArgumentException) { stream[-1..0] }

 stream = ['foo','bar','baz'].stream()
 shouldFail(IllegalArgumentException) { stream[0..-1] }

 stream = ['foo','bar','baz'].stream()
 assert stream[0..<1] == ['foo']

 stream = ['foo','bar','baz'].stream()
 assert stream[1..<2] == ['bar']

 stream = ['foo','bar','baz'].stream()
 assert stream[2..<3] == ['baz']

 stream = ['foo','bar','baz'].stream()
 assert stream[3..<4] == []

 stream = ['foo','bar','baz'].stream()
 assert stream[0<..2] == ['bar','baz']

 stream = ['foo','bar','baz'].stream()
 assert stream[0..99] == ['foo','bar','baz']
      Throws:
      IllegalArgumentException - for negative index or reverse range
      Since:
      5.0.0

    • getAt

      public static <T> List<T> getAt(Stream<T> self, EmptyRange range)
      Returns an empty list. 

       import java.util.stream.Stream
 Stream<String> stream = ['foo','bar','baz'].stream()
 assert stream[1..<1].isEmpty()
      Since:
      5.0.0

    • from

      public static <T> Stream<T> from(Stream<T> self, IntRange range)
      Returns a (possibly empty) stream.

      This is a short-circuiting intermediate operation. 

       import java.util.stream.Stream
 import static groovy.test.GroovyAssert.shouldFail

 Stream<String> stream = ['foo','bar','baz'].stream()
 shouldFail(IllegalArgumentException) { stream.from(-1..0) }

 stream = ['foo','bar','baz'].stream()
 shouldFail(IllegalArgumentException) { stream.from(0..-1) }

 stream = ['foo','bar','baz'].stream()
 assert stream.from(0..<1).toList() == ['foo']

 stream = ['foo','bar','baz'].stream()
 assert stream.from(1..<2).toList() == ['bar']

 stream = ['foo','bar','baz'].stream()
 assert stream.from(2..<3).toList() == ['baz']

 stream = ['foo','bar','baz'].stream()
 assert stream.from(3..<4).toList() == []

 stream = ['foo','bar','baz'].stream()
 assert stream.from(0<..2).toList() == ['bar','baz']

 stream = ['foo','bar','baz'].stream()
 assert stream.from(0<..<2).toList() == ['bar']

 stream = ['foo','bar','baz'].stream()
 assert stream.from(0..99).toList() == ['foo','bar','baz']
      Throws:
      IllegalArgumentException - for negative index or reverse range
      Since:
      5.0.0

    • from

      public static <T> Stream<T> from(Stream<T> self, EmptyRange range)
      Returns an empty stream. 

       import java.util.stream.Stream
 Stream<String> stream = ['foo','bar','baz'].stream()
 assert !stream.from(1..<1).findAny().isPresent()
      Since:
      5.0.0

    • plus

      public static <T> Stream<T> plus(Stream<? extends T> lhs, Collection<? extends T> rhs)
      Returns a lazily concatenated stream whose elements are all the elements of this stream followed by all the elements of the Collection object. 
       import java.util.stream.Stream
 assert (Stream.of(1) + [2]).toList() == [1,2]
 assert (Stream.of(1) + []).toList() == [1]
      Since:
      4.0.0

    • plus

      public static <T> Stream<T> plus(Stream<? extends T> lhs, Iterable<? extends T> rhs)
      Returns a lazily concatenated stream whose elements are all the elements of this stream followed by all the elements of the Iterable object. 
       import java.util.stream.Stream
 assert (Stream.of(1) + [2]).toList() == [1,2]
 assert (Stream.of(1) + []).toList() == [1]
      Since:
      4.0.0

    • plus

      public static <T> Stream<T> plus(Stream<? extends T> lhs, Stream<? extends T> rhs)
      Returns a lazily concatenated stream whose elements are all the elements of this stream followed by all the elements of the second stream. 
       import java.util.stream.Stream
 assert (Stream.of(1) + Stream.<Integer>empty()).toList() == [1]
 assert (Stream.of(1) + Stream.of(2)).toList() == [1,2]
 assert (Stream.of(1) + [2].stream()).toList() == [1,2]
      Since:
      4.0.0

    • stream

      public static <T> Stream<T> stream(T self)
      Returns a sequential Stream containing a single element. 
       def item = 'string'
 assert item.stream().toList() == ['string']
 assert item.stream().findFirst().isPresent()
      Since:
      3.0.0

    • stream

      public static <T> Stream<T> stream(T[] self)
      Returns a sequential Stream with the specified array as its source.
      Type Parameters:
      T - The type of the array elements
      Parameters:
      self - The array, assumed to be unmodified during use
      Returns:
      a Stream for the array
      Since:
      2.5.0

    • stream

      public static Stream<Integer> stream(int[] self)
      Returns a sequential Stream with the specified array as its source.
      Parameters:
      self - The array, assumed to be unmodified during use
      Returns:
      a Stream for the array
      Since:
      2.5.0

    • stream

      public static Stream<Long> stream(long[] self)
      Returns a sequential Stream with the specified array as its source.
      Parameters:
      self - The array, assumed to be unmodified during use
      Returns:
      a Stream for the array
      Since:
      2.5.0

    • stream

      public static Stream<Double> stream(double[] self)
      Returns a sequential Stream with the specified array as its source.
      Parameters:
      self - The array, assumed to be unmodified during use
      Returns:
      a Stream for the array
      Since:
      2.5.0

    • stream

      public static Stream<Character> stream(char[] self)
      Returns a sequential Stream with the specified array as its source.
      Parameters:
      self - The array, assumed to be unmodified during use
      Returns:
      a Stream for the array
      Since:
      2.5.0

    • stream

      public static Stream<Byte> stream(byte[] self)
      Returns a sequential Stream with the specified array as its source.
      Parameters:
      self - The array, assumed to be unmodified during use
      Returns:
      a Stream for the array
      Since:
      2.5.0

    • stream

      public static Stream<Short> stream(short[] self)
      Returns a sequential Stream with the specified array as its source.
      Parameters:
      self - The array, assumed to be unmodified during use
      Returns:
      a Stream for the array
      Since:
      2.5.0

    • stream

      public static Stream<Boolean> stream(boolean[] self)
      Returns a sequential Stream with the specified array as its source.
      Parameters:
      self - The array, assumed to be unmodified during use
      Returns:
      a Stream for the array
      Since:
      2.5.0

    • stream

      public static Stream<Float> stream(float[] self)
      Returns a sequential Stream with the specified array as its source.
      Parameters:
      self - The array, assumed to be unmodified during use
      Returns:
      a Stream for the array
      Since:
      2.5.0

    • stream

      public static <T> Stream<T> stream(Enumeration<T> self)
      Returns a sequential Stream with the specified element(s) as its source. 
       def tokens = new StringTokenizer('one two')
 assert tokens.stream().toList() == ['one', 'two']
      Since:
      3.0.0

    • stream

      public static <T> Stream<T> stream(Iterable<T> self)
      Returns a sequential Stream with the specified element(s) as its source. 
       class Items implements Iterable {
   Iterator<String> iterator() {
     ['one', 'two'].iterator()
   }
 }
 def items = new Items()
 assert items.stream().toList() == ['one', 'two']
      Since:
      3.0.0

    • stream

      public static <T> Stream<T> stream(Iterator<T> self)
      Returns a sequential Stream with the specified element(s) as its source. 
       [].iterator().stream().toList().isEmpty()
 ['one', 'two'].iterator().stream().toList() == ['one', 'two']
      Since:
      3.0.0

    • stream

      public static <T> Stream<T> stream(Spliterator<T> self)
      Returns a sequential Stream with the specified element(s) as its source. 
       assert [].spliterator().stream().toList().isEmpty()
 assert ['one', 'two'].spliterator().stream().toList() == ['one', 'two']
      Since:
      3.0.0

    • stream

      public static <T> Stream<T> stream(NullObject self)
      Returns an empty sequential Stream. 
       def item = null
 assert item.stream().toList() == []
 assert !item.stream().findFirst().isPresent()
      Since:
      3.0.0

    • stream

      public static <T> Stream<T> stream(Optional<T> self)
      If a value is present in the Optional, returns a Stream with the value as its source or else an empty stream.
      Since:
      3.0.0

    • stream

      public static IntStream stream(OptionalInt self)
      If a value is present in the OptionalInt, returns an IntStream with the value as its source or else an empty stream.
      Since:
      3.0.0

    • stream

      public static LongStream stream(OptionalLong self)
      If a value is present in the OptionalLong, returns a LongStream with the value as its source or else an empty stream.
      Since:
      3.0.0

    • stream

      public static DoubleStream stream(OptionalDouble self)
      If a value is present in the OptionalDouble, returns a DoubleStream with the value as its source or else an empty stream.
      Since:
      3.0.0

    • intStream

      public static IntStream intStream(int[] self)
      Returns a sequential IntStream with the specified array as its source.
      Parameters:
      self - The array, assumed to be unmodified during use
      Returns:
      a Stream for the array
      Since:
      3.0.8

    • longStream

      public static LongStream longStream(long[] self)
      Returns a sequential LongStream with the specified array as its source.
      Parameters:
      self - The array, assumed to be unmodified during use
      Returns:
      a Stream for the array
      Since:
      3.0.8

    • doubleStream

      public static DoubleStream doubleStream(double[] self)
      Returns a sequential DoubleStream with the specified array as its source.
      Parameters:
      self - The array, assumed to be unmodified during use
      Returns:
      a Stream for the array
      Since:
      3.0.8

    • size

      public static long size(Stream<?> self)
      An alias for count. Returns the count of elements for this stream. This is a terminal operator and, depending on the underlying stream, may invoke the stream pipeline, leaving it empty after this call. Care should be taken with stream pipelines that have side effects. This method should not be called on an infinite stream. 
       assert [1, 2, 3].stream().size() == 3
      Parameters:
      self - A Stream
      Returns:
      the count of elements in this stream
      Since:
      5.0.0
      See Also:

    • size

      public static long size(IntStream self)
      An alias for count. Returns the count of elements for this stream. This is a terminal operator and, depending on the underlying stream, may invoke the stream pipeline, leaving it empty after this call. Care should be taken with stream pipelines that have side effects. This method should not be called on an infinite stream. 
       int[] nums = [1, 2, 3]
 assert nums.intStream().size() == 3
      Parameters:
      self - An IntStream
      Returns:
      the count of elements in this stream
      Since:
      5.0.0
      See Also:

    • size

      public static long size(LongStream self)
      An alias for count. Returns the count of elements for this stream. This is a terminal operator and, depending on the underlying stream, may invoke the stream pipeline, leaving it empty after this call. Care should be taken with stream pipelines that have side effects. This method should not be called on an infinite stream. 
       long[] nums = [1, 2, 3]
 assert nums.longStream().size() == 3
      Parameters:
      self - A LongStream
      Returns:
      the count of elements in this stream
      Since:
      5.0.0
      See Also:

    • size

      public static long size(DoubleStream self)
      An alias for count. Returns the count of elements for this stream. This is a terminal operator and, depending on the underlying stream, may invoke the stream pipeline, leaving it empty after this call. Care should be taken with stream pipelines that have side effects. This method should not be called on an infinite stream. 
       double[] nums = [1.0d, 2.0d, 3.0d]
 assert nums.doubleStream().size() == 3
      Parameters:
      self - A DoubleStream
      Returns:
      the count of elements in this stream
      Since:
      5.0.0
      See Also:

    • toArray

      public static <T> T[] toArray(Stream<? extends T> self, Class<T> type)
      Returns an array containing the elements of the stream. 
       import static groovy.test.GroovyAssert.shouldFail

 assert Arrays.equals([].stream().toArray(Object), new Object[0])
 assert Arrays.equals([].stream().toArray(String), new String[0])
 assert Arrays.equals([].stream().toArray(String[]), new String[0][])
 assert Arrays.equals(['x'].stream().toArray(Object), ['x'].toArray())
 assert Arrays.equals(['x'].stream().toArray(String), ['x'] as String[])
 assert Arrays.deepEquals([['x'] as String[]].stream().toArray(String[]), [['x'] as String[]] as String[][])
 assert Arrays.equals(['x'].stream().toArray(CharSequence), ['x'] as CharSequence[])

 shouldFail(ArrayStoreException) {
     ['x'].stream().toArray(Thread)
 }

 shouldFail(IllegalArgumentException) {
     ['x'].stream().toArray((Class) null)
 }

 // Stream#toArray(IntFunction) should still be used for closure literal:
 assert Arrays.equals(['x'].stream().toArray { n -> new String[n] }, ['x'] as String[])

 // Stream#toArray(IntFunction) should still be used for method reference:
 assert Arrays.equals(['x'].stream().toArray(String[]::new), ['x'] as String[])
      Parameters:
      self - the stream
      type - the array element type
      Since:
      3.0.4

    • toList

      @Deprecated(since="6.0.0") public static <T> List<T> toList(Stream<T> self)
      Deprecated.
      since 6.0.0; the native Stream.toList() (JDK 16+) shadows this and returns an unmodifiable list. If you need a mutable list, call toMutableList(Stream); otherwise use stream.toList() directly (faster than this extension because it skips the Collectors path).
      Accumulates the elements of stream into a new mutable List.

      Note: since JDK 16, Stream has a native toList() method that returns an unmodifiable list. Java instance methods take precedence over GDK extensions in both @CompileStatic and dynamic dispatch, so stream.toList() now resolves to the native call and yields an immutable result — not a fresh ArrayList as it did pre-JDK 16. Direct callers of this extension method are pointed at the explicit replacements; see the deprecation note.

      Type Parameters:
      T - the type of element
      Parameters:
      self - the stream
      Returns:
      a new mutable java.util.List instance
      Since:
      2.5.0

    • toList

      public static <T> List<T> toList(BaseStream<T,? extends BaseStream> self)
      Accumulates the elements of stream into a new List.
      Type Parameters:
      T - the type of element
      Parameters:
      self - the java.util.stream.BaseStream
      Returns:
      a new java.util.List instance
      Since:
      2.5.0

    • toSet

      public static <T> Set<T> toSet(Stream<T> self)
      Accumulates the elements of stream into a new Set.
      Type Parameters:
      T - the type of element
      Parameters:
      self - the stream
      Returns:
      a new java.util.Set instance
      Since:
      2.5.0

    • toSet

      public static <T> Set<T> toSet(BaseStream<T,? extends BaseStream> self)
      Accumulates the elements of stream into a new Set.
      Type Parameters:
      T - the type of element
      Parameters:
      self - the java.util.stream.BaseStream
      Returns:
      a new java.util.Set instance
      Since:
      2.5.0

    • toMutableList

      public static <T> List<T> toMutableList(Stream<T> self)
      Accumulates the elements of stream into a new mutable List.

      Explicit alternative to the native Stream.toList() (which returns an unmodifiable list since JDK 16). Use this when you need to add to, remove from, or sort the returned list. The returned list is a concrete ArrayList — the cached collector pins the supplier so this is contract, not happenstance. 

       import java.util.stream.Stream
 import org.codehaus.groovy.runtime.StreamGroovyMethods
 def list = StreamGroovyMethods.toMutableList(Stream.of('a', 'b'))
 assert list == ['a', 'b']
 list << 'c'   // mutable — no UnsupportedOperationException
 assert list == ['a', 'b', 'c']
      Type Parameters:
      T - the type of element
      Parameters:
      self - the stream
      Returns:
      a new mutable java.util.List instance
      Since:
      6.0.0

    • toMutableList

      public static <T> List<T> toMutableList(BaseStream<T,? extends BaseStream> self)
      Accumulates the elements of stream into a new mutable List.

      Explicit-mutability alias for toList(BaseStream), symmetric with toMutableList(Stream).

      Type Parameters:
      T - the type of element
      Parameters:
      self - the java.util.stream.BaseStream
      Returns:
      a new mutable java.util.List instance
      Since:
      6.0.0

    • toMutableSet

      public static <T> Set<T> toMutableSet(Stream<T> self)
      Accumulates the elements of stream into a new mutable Set.

      Explicit-mutability alias for toSet(Stream). Provided defensively so user intent stays unambiguous if a future JDK release adds a native Stream.toSet() (which would shadow the GDK extension the way native Stream.toList() did in JDK 16).

      Type Parameters:
      T - the type of element
      Parameters:
      self - the stream
      Returns:
      a new mutable java.util.Set instance
      Since:
      6.0.0

    • toMutableSet

      public static <T> Set<T> toMutableSet(BaseStream<T,? extends BaseStream> self)
      Accumulates the elements of stream into a new mutable Set.

      Explicit-mutability alias for toSet(BaseStream), symmetric with toMutableSet(Stream).

      Type Parameters:
      T - the type of element
      Parameters:
      self - the java.util.stream.BaseStream
      Returns:
      a new mutable java.util.Set instance
      Since:
      6.0.0

    • toImmutableList

      public static <T> List<T> toImmutableList(BaseStream<T,? extends BaseStream> self)
      Accumulates the elements of stream into an immutable List.
      Type Parameters:
      T - the type of element
      Parameters:
      self - the java.util.stream.BaseStream
      Returns:
      an immutable java.util.List instance
      Since:
      6.0.0

    • toImmutableSet

      public static <T> Set<T> toImmutableSet(Stream<T> self)
      Accumulates the elements of stream into an immutable Set.

      No native Stream.toSet() exists, so this provides the immutable counterpart to toSet(Stream). Null elements are preserved (unlike Collectors.toUnmodifiableSet() which rejects nulls); the returned set is unmodifiable and mutation attempts throw UnsupportedOperationException. Returns the canonical empty set (Collections.emptySet()) when the stream is empty. 

       import java.util.stream.Stream
 import static groovy.test.GroovyAssert.shouldFail
 import static org.codehaus.groovy.runtime.StreamGroovyMethods.toImmutableSet
 def set = toImmutableSet(Stream.of('a', null, 'b', 'a'))
 assert set == ['a', null, 'b'] as Set
 shouldFail(UnsupportedOperationException) { set << 'c' }
 assert toImmutableSet(Stream.<String>empty()) === Collections.emptySet()
      Type Parameters:
      T - the type of element
      Parameters:
      self - the stream
      Returns:
      an immutable java.util.Set instance
      Since:
      6.0.0

    • toImmutableSet

      public static <T> Set<T> toImmutableSet(BaseStream<T,? extends BaseStream> self)
      Accumulates the elements of stream into an immutable Set.

      See toImmutableSet(Stream) for the null-tolerance and empty-set semantics — this overload is the BaseStream counterpart with the same contract.

      Type Parameters:
      T - the type of element
      Parameters:
      self - the java.util.stream.BaseStream
      Returns:
      an immutable java.util.Set instance
      Since:
      6.0.0