Example usage for java.util List stream

Introduction

In this page you can find the example usage for java.util List stream.

Prototype

default Stream<E> stream()

Source Link

Document

Returns a sequential Stream with this collection as its source.

Usage

From source file:Main.java

public static void main(String[] args) {
    List<String> names = Arrays.asList("XML", "HTML", "Java", "Javascript", "CSS", "C");

    Function<String, Predicate<String>> startsWithLetter = letter -> name -> name.startsWith(letter);

    names.stream().filter(startsWithLetter.apply("J")).forEach(System.out::println);
}

From source file:Main.java

public static void main(String[] args) throws Exception {
    List<Person> persons = Arrays.asList(new Person("Max", 18), new Person("Peter", 23),
            new Person("Pamela", 23), new Person("David", 12));

    Person result = persons.stream().reduce(new Person("", 0), (p1, p2) -> {
        p1.age += p2.age;/* w w w.  j a v  a 2 s.  c om*/
        p1.name += p2.name;
        return p1;
    });

    System.out.format("name=%s; age=%s", result.name, result.age);
}

From source file:Main.java

public static void main(String[] args) throws Exception {
    List<Person> persons = Arrays.asList(new Person("Max", 18), new Person("Peter", 23),
            new Person("Pamela", 23), new Person("David", 12));

    List<Person> filtered = persons.stream().filter(p -> p.name.startsWith("P")).collect(Collectors.toList());

    System.out.println(filtered); // [Peter, Pamela]
}

From source file:Main.java

public static void main(String[] argv) {
    List<Person> persons = Arrays.asList(new Person("Joe", 12), new Person("Jim", 34), new Person("John", 23));

    Stream<MyWrapper> stream = persons.stream().filter(p -> p.getAge() > 18).map(p -> new MyWrapper(p));

    System.out.println(stream.count());

}

From source file:Main.java

public static void main(String[] args) throws Exception {
    List<Person> persons = Arrays.asList(new Person("Max", 18), new Person("Peter", 23),
            new Person("Pamela", 23), new Person("David", 12));
    Map<Integer, String> map = persons.stream()
            .collect(Collectors.toMap(p -> p.age, p -> p.name, (name1, name2) -> name1 + ";" + name2));

    System.out.println(map);//w  w  w  .  j a v a 2s.c o  m
}

From source file:Main.java

public static void main(String[] args) throws Exception {
    List<Person> persons = Arrays.asList(new Person("Max", 18), new Person("Peter", 23),
            new Person("Pamela", 23), new Person("David", 12));

    Integer ageSum = persons.stream().reduce(0, (sum, p) -> {
        System.out.format("accumulator: sum=%s; person=%s\n", sum, p);
        return sum += p.age;
    }, (sum1, sum2) -> {//from  www.  j av  a  2  s  .  com
        System.out.format("combiner: sum1=%s; sum2=%s\n", sum1, sum2);
        return sum1 + sum2;
    });

    System.out.println(ageSum);
}

From source file:Main.java

public static void main(String[] args) throws Exception {
    List<Person> persons = Arrays.asList(new Person("Max", 18), new Person("Peter", 23),
            new Person("Pamela", 23), new Person("David", 12));

    IntSummaryStatistics ageSummary = persons.stream().collect(Collectors.summarizingInt(p -> p.age));

    System.out.println(ageSummary);
}

From source file:Main.java

public static void main(String[] args) throws Exception {
    List<Person> persons = Arrays.asList(new Person("Max", 18), new Person("Peter", 23),
            new Person("Pamela", 23), new Person("David", 12));

    Map<Integer, List<Person>> personsByAge = persons.stream().collect(Collectors.groupingBy(p -> p.age));

    personsByAge.forEach((age, p) -> System.out.format("age %s: %s\n", age, p));
}

From source file:Main.java

public static void main(String[] argv) throws Exception {
    List<String> argList = Arrays.asList("help", "v");

    Predicate<String> isHelp = (s) -> s.matches("(h|help)");
    Predicate<String> isVerbose = (s) -> s.matches("(v|verbose)");

    boolean needsHelp = argList.stream().anyMatch(isHelp);
    System.out.println(needsHelp);

    boolean verbose = argList.stream().anyMatch(isVerbose);
    System.out.println(verbose);/*from w w w .j  av a 2  s.  com*/
}

From source file:Main.java

public static void main(String[] args) {

    List<String> friends = Arrays.asList("CSS", "HTML", "Oracle", "Dart");

    //same but reverse
    System.out.println("\nsort reverse:");
    Comparator<String> comp = (aName, bName) -> aName.compareTo(bName);

    friends.stream().sorted(comp.reversed()).forEach(System.out::println);
}