Java 8 – How to convert Iterator to Stream

Author: java-w3schools

src/main/java/com/javaprogramto/java8/streams/conversions/IteratorToStream.java

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+package com.javaprogramto.java8.streams.conversions;
+
+import com.javaprogramto.models.Employee;
+
+import java.util.*;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+import java.util.stream.StreamSupport;
+
+public class IteratorToStream {
+
+    public static void main(String[] args) {
+
+        List<Employee> list = new ArrayList<>();
+
+        list.add(new Employee(100, "Santa Clara", 30));
+        list.add(new Employee(101, "Sameera Bell", 25));
+        list.add(new Employee(102, "Jhon Cena", 33));
+        list.add(new Employee(103, "Tubel Nohn", 35));
+        list.add(new Employee(104, "Meen Joseph", 31));
+
+        System.out.println("original List : " + list);
+
+        /*
+        List to Iterator
+         */
+        Iterator<Employee> it = list.iterator();
+
+        /*
+        Iterator to Spliterator
+         */
+        Spliterator<Employee> employeeSpliterator = Spliterators.spliteratorUnknownSize(it, Spliterator.ORDERED);
+
+        /*
+        Spliterator to Stream
+         */
+        Stream<Employee> employeeStream = StreamSupport.stream(employeeSpliterator, false);
+
+
+        List<Employee> ageGt30List = employeeStream.peek(e -> System.out.println(e)).filter(e -> e.getAge() > 30).collect(Collectors.toList());
+
+        System.out.println("Employee age > 30 size: " + ageGt30List.size());
+        System.out.println("Employee age > 30 : " + ageGt30List);
+
+
+    }
+}

src/main/java/com/javaprogramto/java8/streams/conversions/IteratorToStreamUtility.java

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+package com.javaprogramto.java8.streams.conversions;
+
+import com.javaprogramto.models.Employee;
+
+import java.util.*;
+import java.util.stream.Stream;
+import java.util.stream.StreamSupport;
+
+public class IteratorToStreamUtility {
+
+    public static void main(String[] args) {
+
+        List<Employee> list = new ArrayList<>();
+
+        list.add(new Employee(200, "Momanth Soraga", 30));
+        list.add(new Employee(201, "Fidha Lady", 25));
+
+        Stream<Employee> empStream = convertIteratorToStream(list);
+
+
+        System.out.println("Employee Stream Count : " + empStream.count());
+
+        List<Integer> intList = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9);
+
+        Stream<Integer> intStream  = convertIteratorToStream(intList);
+
+        System.out.println("Integer Stream Count : " + intStream.count());
+
+        List<String> countiresList = Arrays.asList("USA", "India","UK","AUS");
+
+        Stream<String> countiresStream  = convertIteratorToStream(countiresList);
+
+        System.out.println("String countries Stream Count : " + countiresStream.count());
+
+
+
+    }
+
+    /**
+     * Generic method to take any value List type and return a generic Stream.
+     * <p>
+     * Main goal to convert Iterator to Stream.
+     *
+     * @param source
+     * @param <T>
+     * @return
+     */
+    public static <T> Stream<T> convertIteratorToStream(List<T> source) {
+
+         /*
+        List to Iterator
+         */
+        Iterator<T> it = source.iterator();
+
+        /*
+        Iterator to Spliterator
+         */
+        Spliterator<T> spliterator = Spliterators.spliteratorUnknownSize(it, Spliterator.ORDERED);
+
+        /*
+        Spliterator to Stream
+         */
+        Stream<T> oututStream = StreamSupport.stream(spliterator, false);
+
+        return oututStream;
+    }
+}