Java 8 Stream Examples

public class Java8Tester {
   public static void main(String args[]){
      System.out.println("Using Java 7: ");
    
      // Count empty strings
      List<String> strings = Arrays.asList("abc", "", "bc", "efg", "abcd","", "jkl");
      System.out.println("List: " +strings);
      long count = getCountEmptyStringUsingJava7(strings);
    
      System.out.println("Empty Strings: " + count);
      count = getCountLength3UsingJava7(strings);
    
      System.out.println("Strings of length 3: " + count);
    
      //Eliminate empty string
      List<String> filtered = deleteEmptyStringsUsingJava7(strings);
      System.out.println("Filtered List: " + filtered);
    
      //Eliminate empty string and join using comma.
      String mergedString = getMergedStringUsingJava7(strings,", ");
      System.out.println("Merged String: " + mergedString);
      List<Integer> numbers = Arrays.asList(3, 2, 2, 3, 7, 3, 5);
    
      //get list of square of distinct numbers
      List<Integer> squaresList = getSquares(numbers);
      System.out.println("Squares List: " + squaresList);
      List<Integer> integers = Arrays.asList(1,2,13,4,15,6,17,8,19);
    
      System.out.println("List: " +integers);
      System.out.println("Highest number in List : " + getMax(integers));
      System.out.println("Lowest number in List : " + getMin(integers));
      System.out.println("Sum of all numbers : " + getSum(integers));
      System.out.println("Average of all numbers : " + getAverage(integers));
      System.out.println("Random Numbers: ");
    
      //print ten random numbers
      Random random = new Random();
    
      for(int i=0; i < 10; i++){
         System.out.println(random.nextInt());
      }
    
      System.out.println("Using Java 8: ");
      System.out.println("List: " +strings);
    
      count = strings.stream().filter(string->string.isEmpty()).count();
      System.out.println("Empty Strings: " + count);
    
      count = strings.stream().filter(string -> string.length() == 3).count();
      System.out.println("Strings of length 3: " + count);
    
      filtered = strings.stream().filter(string ->!string.isEmpty()).collect(Collectors.toList());
      System.out.println("Filtered List: " + filtered);
    
      mergedString = strings.stream().filter(string ->!string.isEmpty()).collect(Collectors.joining(", "));
      System.out.println("Merged String: " + mergedString);
    
      squaresList = numbers.stream().map( i ->i*i).distinct().collect(Collectors.toList());
      System.out.println("Squares List: " + squaresList);
      System.out.println("List: " +integers);
    
      IntSummaryStatistics stats = integers.stream().mapToInt((x) ->x).summaryStatistics();
    
      System.out.println("Highest number in List : " + stats.getMax());
      System.out.println("Lowest number in List : " + stats.getMin());
      System.out.println("Sum of all numbers : " + stats.getSum());
      System.out.println("Average of all numbers : " + stats.getAverage());
      System.out.println("Random Numbers: ");
    
      random.ints().limit(10).sorted().forEach(System.out::println);
    
      //parallel processing
      count = strings.parallelStream().filter(string -> string.isEmpty()).count();
      System.out.println("Empty Strings: " + count);
   }
  
   private static int getCountEmptyStringUsingJava7(List<String> strings){
      int count = 0;
    
      for(String string: strings){
    
         if(string.isEmpty()){
            count++;
         }
      }
      return count;
   }
  
   private static int getCountLength3UsingJava7(List<String> strings){
      int count = 0;
    
      for(String string: strings){
    
         if(string.length() == 3){
            count++;
         }
      }
      return count;
   }
  
   private static List<String> deleteEmptyStringsUsingJava7(List<String> strings){
      List<String> filteredList = new ArrayList<String>();
    
      for(String string: strings){
    
         if(!string.isEmpty()){
             filteredList.add(string);
         }
      }
      return filteredList;
   }
  
   private static String getMergedStringUsingJava7(List<String> strings, String separator){
      StringBuilder stringBuilder = new StringBuilder();
    
      for(String string: strings){
    
         if(!string.isEmpty()){
            stringBuilder.append(string);
            stringBuilder.append(separator);
         }
      }
      String mergedString = stringBuilder.toString();
      return mergedString.substring(0, mergedString.length()-2);
   }
  
   private static List<Integer> getSquares(List<Integer> numbers){
      List<Integer> squaresList = new ArrayList<Integer>();
    
      for(Integer number: numbers){
         Integer square = new Integer(number.intValue() * number.intValue());
      
         if(!squaresList.contains(square)){
            squaresList.add(square);
         }
      }
      return squaresList;
   }
  
   private static int getMax(List<Integer> numbers){
      int max = numbers.get(0);
    
      for(int i=1;i < numbers.size();i++){
    
         Integer number = numbers.get(i);
      
         if(number.intValue() > max){
            max = number.intValue();
         }
      }
      return max;
   }
  
   private static int getMin(List<Integer> numbers){
      int min = numbers.get(0);
    
      for(int i=1;i < numbers.size();i++){
         Integer number = numbers.get(i);
    
         if(number.intValue() < min){
            min = number.intValue();
         }
      }
      return min;
   }
  
   private static int getSum(List numbers){
      int sum = (int)(numbers.get(0));
    
      for(int i=1;i < numbers.size();i++){
         sum += (int)numbers.get(i);
      }
      return sum;
   }
  
   private static int getAverage(List<Integer> numbers){
      return getSum(numbers) / numbers.size();
   }
}

 

References
https://www.tutorialspoint.com/java8/java8_streams.htm
http://www.drdobbs.com/jvm/lambdas-and-streams-in-java-8-libraries/240166818