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Commit 890f3fc

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package StreamCollectors;
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import java.util.Arrays;
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import java.util.stream.Stream;
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import java.util.List;
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public class CollectStreamElementsToArray
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{
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public static void main(String[] args)
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{
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List<Integer> list = Arrays.asList(1,2,3,4,5,6,7,8,9,10);
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Stream<Integer> stream = list.stream();
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Integer[] evenNumbersArr = stream.filter(i -> i%2 == 0).toArray(Integer[]::new);
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for(Integer num:evenNumbersArr)
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{
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System.out.print(num+" ");
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}
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}
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}
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package StreamCollectors;
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import java.util.LinkedHashMap;
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import java.util.Map;
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import java.util.stream.Collectors;
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import java.util.stream.Stream;
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class Student
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{
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private int ID;
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private String Name;
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Student(int ID,String Name)
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{
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this.ID=ID;
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this.Name=Name;
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}
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public int getID()
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{
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return ID;
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}
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public void setID(int iD)
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{
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ID = iD;
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}
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public String getName()
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{
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return Name;
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}
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public void setName(String name)
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{
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Name = name;
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}
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}
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public class CollectStreamElementsToMap
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{
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public static void main(String[] args)
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{
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Stream<Student> stream = Stream.of(new Student(1,"Ram"),new Student(2,"Arjun"),new Student(3,"Kavi"),new Student(4,"Sanju"),new Student(5,"Ajay"));
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Map<Integer,String> map = stream.collect(Collectors.toMap(Student::getID,Student::getName));
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System.out.println("Original Value:");
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for(Map.Entry<Integer,String> m:map.entrySet())
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{
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System.out.println(m.getKey()+" "+m.getValue());
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}
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//sort map based on key
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Map<Integer,String> result1 = new LinkedHashMap<>();
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map.entrySet().stream()
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.sorted(Map.Entry.comparingByKey())
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.forEachOrdered(x -> result1.put(x.getKey(), x.getValue()));
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System.out.println("Sort By Key:" + result1);
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//sort map based on Value
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Map<Integer,String> result2 = new LinkedHashMap<>();
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map.entrySet().stream()
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.sorted(Map.Entry.comparingByValue())
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.forEachOrdered(x -> result2.put(x.getKey(), x.getValue()));
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System.out.println("Sort By Value:" + result2);
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}
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}
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package StreamCollectors;
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import java.util.Arrays;
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import java.util.Collections;
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import java.util.List;
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import java.util.LinkedHashSet;
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import java.util.HashSet;
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import java.util.TreeSet;
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import java.util.Set;
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import java.util.stream.Collectors;
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import java.util.stream.Stream;
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public class CollectStreamElementsToSet
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{
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public static void main(String[] args)
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{
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//convert stream to set
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List<Integer> list = Arrays.asList(1,2,3,4,5,4,5,8,9,10);
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Stream<Integer> stream = list.stream();
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Set<Integer> set = stream.collect(Collectors.toSet());
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System.out.println(set);
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//convert stream to an array and them array into set
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List<Integer> list1 = Arrays.asList(1,2,4,3,5,4,5,8,8,7);
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Stream<Integer> stream1 = list1.stream();
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Integer[] arr = stream1.toArray(Integer[]::new);
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//random order set
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Set<Integer> set1 = new HashSet<>();
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Collections.addAll(set1, arr);
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System.out.println(set1);
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//insertion order set
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Set<Integer> set2 = new LinkedHashSet<>();
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Collections.addAll(set2, arr);
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System.out.println(set2);
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//sorted order set
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Set<Integer> set3 = new TreeSet<>();
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Collections.addAll(set3, arr);
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System.out.println(set3);
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}
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}
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package StreamCollectors;
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import java.util.Arrays;
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import java.util.List;
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import java.util.stream.Stream;
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import java.util.stream.Collectors;
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public class CollectsreamElementsToList
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{
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public static void main(String[] args)
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{
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List<Integer> list = Arrays.asList(1,2,3,4,5,6,7,8,9,10);
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Stream<Integer> stream = list.stream();
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List<Integer> evenNumbersList = stream.collect(Collectors.toList());
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System.out.print(evenNumbersList);
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}
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}

‎StreamCollectors/SortingStream.java‎

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package StreamCollectors;
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import java.util.Arrays;
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import java.util.Comparator;
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import java.util.List;
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import java.util.stream.Stream;
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public class SortingStream
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{
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public static void main(String[] args)
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{
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//convert stream into set
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List<Integer> list = Arrays.asList(1,2,3,4,5,6,7,8,9,10);
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Stream<Integer> stream1 = list.stream();
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Stream<Integer> stream2 = list.stream();
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//ascending sort
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stream1.sorted().forEach(e -> System.out.print(e+" "));
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System.out.println();
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//descending sort
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stream2.sorted(Comparator.reverseOrder()).forEach(e -> System.out.print(e+" "));
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System.out.println();
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}
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}

‎StreamExamples/DistinctByKeys.java‎

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package StreamExamples;
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import java.util.Arrays;
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import java.util.List;
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import java.util.Map;
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import java.util.concurrent.ConcurrentHashMap;
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import java.util.function.Function;
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import java.util.function.Predicate;
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import java.util.stream.Collectors;
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import java.util.stream.Stream;
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import StudentClass.Student;
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public class DistinctByKeys
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{
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public static void main(String[] args)
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{
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Stream.of(new Student(1,"Ram"),new Student(2,"Arjun"),new Student(3,"Kavi"),new Student(4,"Sanju"),new Student(5,"Ajay"))
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.filter(distinctByKeys(Student::getID, Student::getName))
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.collect(Collectors.toList()).forEach(System.out::println);
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System.out.println();
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}
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private static <T> Predicate<T> distinctByKeys(Function<? super T, ?>... keyExtractors)
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{
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final Map<List<?>, Boolean> seen = new ConcurrentHashMap<>();
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return t ->
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{
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final List<?> keys = Arrays.stream(keyExtractors)
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.map(ke -> ke.apply(t))
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.collect(Collectors.toList());
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return seen.putIfAbsent(keys, Boolean.TRUE) == null;
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};
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}
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}
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package StreamExamples;
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import java.util.Map;
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import java.util.concurrent.ConcurrentHashMap;
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import java.util.function.Function;
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import java.util.function.Predicate;
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import java.util.stream.Collectors;
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import java.util.stream.Stream;
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import StudentClass.CustomKey;
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import StudentClass.Student;
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public class DistinctByMultipleProperties
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{
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public static void main(String[] args)
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{
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Stream.of(new Student(1,"Ram"),new Student(2,"Arjun"),new Student(3,"Kavi"),new Student(4,"Sanju"),new Student(5,"Ajay"))
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.filter(distinctByKey(CustomKey::new))
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.collect(Collectors.toList()).forEach(System.out::println);
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System.out.println();
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}
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public static <T> Predicate<T> distinctByKey(Function<? super T, Object> keyExtractor)
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{
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Map<Object, Boolean> seen = new ConcurrentHashMap<>();
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return t -> seen.putIfAbsent(keyExtractor.apply(t), Boolean.TRUE) == null;
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}
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}

‎StreamExamples/FindLastElement.java‎

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package StreamExamples;
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import java.util.Arrays;
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import java.util.stream.Stream;
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public class FindLastElement
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{
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public static void main(String[] args)
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{
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//using stream.reduce()
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Stream<Integer> stream1 = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9).stream();
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Integer lastElement1 = stream1.reduce((first, second) -> second).orElse(-1);
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System.out.println(lastElement1);
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//or
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Stream<Integer> emptyStream = Stream.empty();
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Integer lastElement2 = emptyStream.reduce((first, second) -> second)
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.orElseThrow(() -> new IllegalStateException("no last element"));
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System.out.println(lastElement2);
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}
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}
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package StreamExamples;
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import java.util.stream.Stream;
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public class FixedLengthStream
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{
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public static void main(String[] args)
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{
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Stream.Builder<Integer> streamBuilder = Stream.builder();
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streamBuilder.accept(1);
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streamBuilder.accept(2);
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streamBuilder.accept(3);
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streamBuilder.accept(4);
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streamBuilder.accept(5);
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streamBuilder.build().forEach(e->System.out.print(e+" "));
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}
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}

‎StreamExamples/InfiniteStream.java‎

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package StreamExamples;
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import java.util.List;
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import java.util.Random;
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import java.util.stream.Collectors;
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import java.util.stream.Stream;
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import StudentClass.Student;
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public class InfiniteStream
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{
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public static void main(String[] args)
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{
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//Infinite stream of random numbers
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List<Integer> randomNumbers = Stream.generate(() -> (new Random()).nextInt(100))
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.limit(10).collect(Collectors.toList());
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System.out.println(randomNumbers);
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//infinite stream of Custom Objects
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List<Student> students = Stream.generate(Student::create)
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.limit(5).collect(Collectors.toList());
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for(Student student:students)
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{
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System.out.println("Student ID : "+student.getID()+" , Student Name : "+student.getName());
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}
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}
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}

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