Blog for coders !!: Java 8 Stream API implementation

import java.util.*;
import java.util.stream.Collectors;
public class TestExe1 {
public static void main(String[] args) {
List<String> myList1 =
Arrays.asList("a1", "a1","a1","a2", "b1", "c2", "c1");
List<String> teamIndia = Arrays.asList("i1", "i2", "i3");
List<String> teamAustralia = Arrays.asList("a1", "a2", "a3");
List<String> teamEngland = Arrays.asList("Alex", "Bell", "Broad");
List<String> teamNewZeland = Arrays.asList("Kane", "Nathan", "Vettori");
List<String> teamSouthAfrica = Arrays.asList("AB", "Amla", "Faf");
List<String> teamWestIndies = Arrays.asList("Sammy", "Gayle", "Narine");
List<String> teamSriLanka = Arrays.asList("Mahela", "Sanga", "Dilshan");
List<String> teamPakistan = Arrays.asList("Misbah", "Afridi", "Shehzad");
List<List<String>> playersInWorldCup2016 = new ArrayList<>();
playersInWorldCup2016.add(teamIndia);
playersInWorldCup2016.add(teamAustralia);
playersInWorldCup2016.add(teamEngland);
playersInWorldCup2016.add(teamNewZeland);
playersInWorldCup2016.add(teamSouthAfrica);
playersInWorldCup2016.add(teamWestIndies);
playersInWorldCup2016.add(teamSriLanka);
playersInWorldCup2016.add(teamPakistan);
// Let's print all players before Java 8
List<String> listOfAllPlayers = new ArrayList<>();
for(List<String> team : playersInWorldCup2016){
for(String name : team){
listOfAllPlayers.add(name);
}
}
System.out.println("Players playing in world cup 2016");
System.out.println(listOfAllPlayers);
List<String> myList =
Arrays.asList("a1", "a1","a1","a2", "b1", "c2", "c1");
// Now let's do this in Java 8 using FlatMap
List<String> flatMapList = playersInWorldCup2016.stream()
.flatMap(x -> x.stream())
.collect(Collectors.toList());
System.out.println("List of all Players using Java 8"); System.out.println(flatMapList);
myList
.stream()
.filter(s1 -> s1.startsWith("c"))
.map(String::toUpperCase)
.sorted()
.skip(1)
.forEach(System.out::println);
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(v -> !(v.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();
}

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Thursday, June 28, 2018

Java 8 Stream API implementation

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