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When a terminal method in invoked on a stream, iteration starts on stream and any other chained stream. Once the iteration is over then the result of terminal method is returned. A terminal method does not return a Stream thus once a terminal method is invoked over a stream then its chaining of non-terminal methods or intermediate methods stops/terminates.
Generally, terminal methods returns a single value and are invoked on each element of the stream. Following are some of the important terminal methods of Stream interface. Each terminal function takes a predicate function, initiates the iterations of elements, apply the predicate on each element.
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anyMatch − If predicate returns true for any of the element, it returns true. If no element matches, false is returned.
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allMatch − If predicate returns false for any of the element, it returns false. If all element matches, true is returned.
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noneMatch − If no element matches, true is returned otherwise false is returned.
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collect − each element is stored into the collection passed.
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count − returns count of elements passed through intermediate methods.
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findAny − returns Optional instance containing any element or empty instance is returned.
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findFirst − returns first element under Optional instance. For empty stream, empty instance is returned.
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forEach − apply the consumer function on each element. Used to print all elements of a stream.
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min − returns the smallest element of the stream. Compares elements based on comparator predicate passed.
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max − returns the largest element of the stream. Compares elements based on comparator predicate passed.
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reduce − reduces all elements to a single element using the predicate passed.
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toArray − returns arrays of elements of stream.
Example – Terminal Methods
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;
public class FunctionTester {
public static void main(String[] args) {
List<String> stringList
= Arrays.asList("One", "Two", "Three", "Four", "Five", "One");
System.out.println("Example - anyMatchn");
//anyMatch - check if Two is present?
System.out.println("Two is present: "
+ stringList
.stream()
.anyMatch(s -> {return s.contains("Two");}));
System.out.println("nExample - allMatchn");
//allMatch - check if length of each string is greater than 2.
System.out.println("Length > 2: "
+ stringList
.stream()
.allMatch(s -> {return s.length() > 2;}));
System.out.println("nExample - noneMatchn");
//noneMatch - check if length of each string is greater than 6.
System.out.println("Length > 6: "
+ stringList
.stream()
.noneMatch(s -> {return s.length() > 6;}));
System.out.println("nExample - collectn");
System.out.println("List: "
+ stringList
.stream()
.filter(s -> {return s.length() > 3;})
.collect(Collectors.toList()));
System.out.println("nExample - countn");
System.out.println("Count: "
+ stringList
.stream()
.filter(s -> {return s.length() > 3;})
.count());
System.out.println("nExample - findAnyn");
System.out.println("findAny: "
+ stringList
.stream()
.findAny().get());
System.out.println("nExample - findFirstn");
System.out.println("findFirst: "
+ stringList
.stream()
.findFirst().get());
System.out.println("nExample - forEachn");
stringList
.stream()
.forEach(System.out::println);
System.out.println("nExample - minn");
System.out.println("min: "
+ stringList
.stream()
.min((s1, s2) -> { return s1.compareTo(s2);}));
System.out.println("nExample - maxn");
System.out.println("min: "
+ stringList
.stream()
.max((s1, s2) -> { return s1.compareTo(s2);}));
System.out.println("nExample - reducen");
System.out.println("reduced: "
+ stringList
.stream()
.reduce((s1, s2) -> { return s1 + ", "+ s2;})
.get());
}
}
Output
Example - anyMatch Two is present: true Example - allMatch Length > 2: true Example - noneMatch Length > 6: true Example - collect List: [Three, Four, Five] Example - count Count: 3 Example - findAny findAny: One Example - findFirst findFirst: One Example - forEach One Two Three Four Five One Example - min min: Optional[Five] Example - max min: Optional[Two] Example - reduce reduced: One, Two, Three, Four, Five, One
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