import java.util.*;

import java.util.stream.Collector;

import java.util.stream.Collectors;

/**

* Created by john on 2016/1/8.

*/

public class Java8StreamExample {

public static void main(String[] args) {

System.out.println("Using Java7");

//Count empty string

List<String> strings = Arrays.asList("abc", "", "bc", "efg", "abcd","", "jkl");

System.out.println("List: " +strings);

long count = getCountEmptyStringUsingJava7(strings);

System.out.println("Empty string: "+count);

count = getCountLength3UsingJava7(strings);

System.out.println("String of length 3:"+count);

//Eliminate empty string

List<String> filtered = deleteEmptyStringUsingJava7(strings);

System.out.println("Filtered List: "+filtered);

//Eliminate empty string and join using comma

String mergeString = getMergedStringUsingJava7(strings,",");

System.out.println("Merged string: "+mergeString);

List<Integer> numbers = Arrays.asList(1,2,13,4,15,6,17,8,19);

System.out.println("List: "+numbers);

System.out.println("The highest number in list: "+getMax(numbers));

System.out.println("The lowest number in list: "+getMin(numbers));

System.out.println("The sum of all numbers: "+getSum(numbers));

System.out.println("The average of all list: "+getAverage(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 Java8");

System.out.println("List: "+strings);

count = strings.stream().filter(string->string.isEmpty()).count();

System.out.println("Empty string: "+count);

count = strings.stream().filter(string->string.length()==3).count();

System.out.println("String of length 3:"+count);

filtered = strings.stream().filter(string->!string.isEmpty()).collect(Collectors.toList());

System.out.println("Filtered List: "+filtered);

mergeString = strings.stream().filter(string->!string.isEmpty()).collect(Collectors.joining(", "));

System.out.println("Merged string: "+mergeString);

IntSummaryStatistics stats = numbers.stream().mapToInt((x)->x).summaryStatistics();

System.out.println("List: "+numbers);

System.out.println("The highest number in list: "+stats.getMax());

System.out.println("The lowest number in list: "+stats.getMin());

System.out.println("The sum of all numbers: "+stats.getSum());

System.out.println("The average of all list: "+stats.getAverage());

random.ints().limit(10).sorted().forEach(System.out::println);

//parallel processing

count = strings.parallelStream().filter(string->string.isEmpty()).count();

System.out.println("Empty string: "+count);

}

private static int getCountEmptyStringUsingJava7(List<String> strings) {

int count =0;

for(String str : strings) {

if(str.isEmpty())

count++;

}

return count;

}

private static int getCountLength3UsingJava7(List<String> strings) {

int count =0;

for(String str : strings) {

if(str.length() == 3) {

count++;

}

}

return count;

}

private static List<String> deleteEmptyStringUsingJava7(List<String> strings) {

List<String> filteredList = new ArrayList<String>();

for(String str : strings) {

if(!str.isEmpty())

filteredList.add(str);

}

return filteredList;

}

// private static String getMergedStringUsingJava7(List<String> strings,String separator) {

// StringBuilder builder = new StringBuilder();

// for(String str : strings) {

// if(!strings.isEmpty()) {

// builder.append(str);

// builder.append(separator);

// }

// }

// String mergedString =builder.toString();

// return mergedString.substring(0,mergedString.length()-2);

// }

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> squares = new ArrayList<Integer>();

for(Integer num : numbers) {

Integer sequare = new Integer(num.intValue() * num.intValue());

if(!squares.contains(sequare))

squares.add(sequare);

}

return squares;

}

private static int getMax(List<Integer> numbers) {

int max = numbers.get(0);

for(Integer num : numbers) {

if(max < num.intValue())

max = num.intValue();

}

return max;

}

private static int getMin(List<Integer> numbers) {

int min = numbers.get(0);

for(Integer num : numbers) {

if(min > num.intValue())

min = num.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();

}

}