Java Streams API Demo Example

StreamUtils.java

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;
import java.util.stream.IntStream;

public class StreamUtils {

  public static void main(String[] args) {

    integerStream();
    sortItOut();
    transformer();


  }


  /**
   * Usage map and collect
   */
  private static void transformer(){
    Map<String,Integer> items = new HashMap();
    items.put("apple",2);
    items.put("banana",5);
    items.put("pineapple",2);
    items.put("chocolate",10);

     List altered = items.entrySet().stream()
         .map(item ->{
           HashMap ele = new HashMap();
           ele.put(item.getKey(),item.getValue()+10);
           return ele;
         })
         .collect(Collectors.toList());

     altered.stream().forEach(System.out::println);


  }

  /**
   * Usage: filter and sort
   */
  private static  void sortItOut(){
    ArrayList<String> names = new ArrayList<String>();
    names.add("didi");
    names.add("dexter");
    names.add("batman");
    names.add("swat cats");
    names.add("iron man");


    names.stream()
        .filter(name -> name.startsWith("d"))
        .sorted()
        .forEach(System.out::println);
  }


  /**
   * Just printit.
   */
  private static void integerStream(){

    IntStream.range(1,9)
        .forEach(System.out::println);

  }

}