Method Detail

• <T> public Stream<T> from(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

• <T> public Stream<T> from(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

• <T> public T getAt(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

• <T> public List<T> getAt(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

• <T> public List<T> getAt(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

• <T> public Stream<T> plus(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

• <T> public Stream<T> plus(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

• <T> public Stream<T> plus(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

• public long size()

  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
   

  Returns:

  the count of elements in this stream

  See Also:

  Stream.count

  Since:

  5.0.0

• <T> public T[] toArray(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:

  type - the array element type

  Since:

  3.0.4

• <T> public Set<T> toImmutableSet()

  Accumulates the elements of stream into an immutable Set.

  No native Stream.toSet() exists, so this provides the immutable counterpart to Stream.toSet. 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

  Returns:

  an immutable java.util.Set instance

  Since:

  6.0.0

• <T> public List<T> toMutableList()

  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

  Returns:

  a new mutable java.util.List instance

  Since:

  6.0.0

• <T> public Set<T> toMutableSet()

  Accumulates the elements of stream into a new mutable Set.

  Explicit-mutability alias for Stream.toSet. 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

  Returns:

  a new mutable java.util.Set instance

  Since:

  6.0.0

• <T> public Set<T> toSet()

  Accumulates the elements of stream into a new Set.

  Type Parameters:

  T - the type of element

  Returns:

  a new java.util.Set instance

  Since:

  2.5.0