Examples for java stream api

java-8/stream-api/ExampleStreamOperation.java

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+import java.util.*;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+public class ExampleStreamOperation {
+    public static void main(String[] args) {
+        // filter()
+        Stream<Integer> intStream = Stream.of(1, 2, 3, 4, 5, 6);
+        Stream<Integer> evenStream = intStream.filter(e -> (e % 2 == 0));
+
+        evenStream.forEach(e -> System.out.print(e+" "));
+
+        //map()
+        Stream<Integer> intStream1 = Stream.of(1, 2, 3, 4, 5, 6);
+        Stream<Integer> mapStream = intStream1.map(e -> e * 10);
+
+        mapStream.forEach(e -> System.out.print(e + " "));
+
+        //sorted()
+        Stream<Integer> intStream3 = Stream.of(4,22,1,7,5,10);
+        Stream<Integer> sortedStream = intStream3.sorted();
+
+        sortedStream.forEach(e -> System.out.print(e + " "));
+
+        //foreach()
+        Stream<Integer> intStream4 = Stream.of(1, 2, 3, 4, 5, 6, 7);
+        intStream4.forEach(e -> System.out.print(e * 3 + " "));
+
+        //using a map :
+        Map<String,Integer> map = new HashMap<>();
+        map.put("a",1);
+        map.put("b",2);
+        map.put("c",3);
+        map.put("d",4);
+        map.forEach((key,value) -> System.out.println("Key: "+key+" Value: "+value));
+
+        //reduce
+        Stream<Integer> intStream5 = Stream.of(1, 2, 3, 4);
+        //reduce will add each element of the stream
+        Optional<Integer> optionalResult = intStream5.reduce((i, j) -> i + j);
+        System.out.println(optionalResult.get());
+
+        //count
+        Stream<Integer> intStream6 = Stream.of(1, 2, 3, 4);
+        System.out.println("Total elements "+intStream6.count());
+
+        //collect()
+        Stream<Integer> intStream7 = Stream.of(1, 2, 3, 4, 5, 6, 7);
+        List<Integer> intList = intStream7.collect(Collectors.toList());
+        System.out.print(intList);
+
+        //match()
+        List<String> strList = new ArrayList<>();
+        strList.add("Sun");
+        strList.add("Mon");
+        strList.add("Tues");
+
+        //check if any value in the list starts with 'T'
+        System.out.println(strList.stream().anyMatch(e -> e.startsWith("T")));
+
+        //check if all values in the list start with 'T'
+        System.out.println(strList.stream().allMatch(e -> e.startsWith("T")));
+
+        //check if none of the values in the list starts with 'X'
+        System.out.println(strList.stream().noneMatch(e -> e.startsWith("X")));
+    }
+}