java stream examples

java stream examples

Author: hmkcode

java-stream/src/main/java/com/hmkcode/App.java

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+package com.hmkcode;
+
+import java.util.Arrays;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+public class App 
+{
+	public static void main( String[] args )
+    {
+    	String[] arr = new String[]{"a", "b", "c", "d"};
+    	Stream<String> stream = Arrays.stream(arr);
+    	
+    	stream = Stream.of("a", "b", "c", "d");
+    	
+    	List<String> list = new LinkedList<String>();
+     	list.add("a");
+     	list.add("b");
+     	stream = list.stream();
+     	
+    	// forEach()
+    	stream = Stream.of("a", "b", "c", "d");
+    	stream.forEach(e -> System.out.println(e));
+    	
+    	// distinct() | count()
+    	stream = Stream.of("a", "b", "c", "d");
+    	System.out.println(stream.distinct().count());
+    	
+    	// anyMatch()
+    	stream = Stream.of("a", "b", "c", "d");
+    	System.out.println(stream.anyMatch(e -> e.contains("a")));
+    	
+    	// filter()
+    	stream = Stream.of("a", "b", "c", "d");
+    	stream.filter(e -> e.contains("b")).forEach(e -> System.out.println(e));
+    	
+    	// map()
+    	stream = Stream.of("a", "b", "c", "d");
+    	stream.map(e -> e.toUpperCase()).forEach(e -> System.out.println(e));
+    	
+    	// flatMap()
+    	stream = getBigList().stream().flatMap(lst -> lst.stream());
+    	stream.forEach(e -> System.out.println(e));
+    	
+    	//[any|all|none]Match()
+    	System.out.println(Stream.of("a", "b", "c", "d").allMatch( e -> (e.length() == 1)));
+    	System.out.println(Stream.of("a", "b", "c", "d").noneMatch(e -> (e.length() == 2)));
+    	System.out.println(Stream.of("a", "b", "c", "d").anyMatch( e ->  e.equals("a") ));
+    	    	
+    	//reduce()
+    	stream = Stream.of("a", "b", "c", "d");
+    	System.out.println(stream.reduce("", (x,y) -> apply(x,y)));
+    	
+    	//collect(Collectors)
+    	stream = Stream.of("a", "b", "c", "d");
+    	System.out.println(stream.collect(Collectors.toList()));
+    	
+    	
+    }   
+   
+    private static String apply(String a, String b){    	
+    	System.out.println(a+"->"+b);
+    	return a+b;
+    }
+    
+    private static List<List<String>> getBigList(){
+    	
+    	List<List<String>> bigList = new LinkedList<List<String>>();
+     	
+     	List<String> list1 = new LinkedList<String>();
+     	list1.add("a");
+     	list1.add("b");
+     	
+     	List<String> list2 = new LinkedList<String>();
+     	list2.add("c");
+     	list2.add("d");
+     	
+     	bigList.add(list1);
+     	bigList.add(list2);
+     
+     	return bigList;
+    }
+
+
+}