<div id="readability-page-1" class="page"><div><div><a rel="noopener" href="/@sindepal?source=post_page-----3c55db2bb906--------------------------------"><img alt="신상훈" src="https://miro.medium.com/fit/c/56/56/0*IyUJXQViJJEmVWaW.jpg" width="28" height="28"></a></div>Java Stream<pre>import java.util.Arrays;import java.util.Comparator;import java.util.List;public class StreamTest2 {public static void main(String[] args) {// jdk 1.9 이상 일경우 List.of 사용// List&lt;Integer&gt; numbers = List.of(1,2,3,4,5,6,7);List&lt;Integer&gt; numbers = Arrays.asList(15,1,2);int sum = beforeAddListStructured(numbers);System.out.println(sum);int sumStream = afterAddListStructured(numbers);System.out.println(sumStream);afterSquaredMethod(numbers);afterSortInAsc(numbers);afterSortInDesc(numbers);}private static int beforeAddListStructured(List&lt;Integer&gt; numbers ) {int sum = 0;for (int number : numbers) {sum += number;}return sum;}// 두개의 파람을 더하는 메소드private static int sum(int aggregate , int nextNumber) {return aggregate + nextNumber;}// 합계private static int afterAddListStructured(List&lt;Integer&gt; numbers ) {// reduce(초기값, 로직)return numbers.stream()// .reduce(0,StreamTest2::sum);// .reduce(0, (x,y) -&gt; x + y);.reduce(0, Integer::sum);}// 시작 숫자 가저오기private static int afterStartNumber( List&lt;Integer&gt; numbers ) {return numbers.stream().reduce(0, (x,y) -&gt; x );}// 마지막 숫자 가져오기private static int afterLastNumber( List&lt;Integer&gt; numbers ) {return numbers.stream().reduce(0, (x,y) -&gt; y );}// 최대 값 가저오기private static int afterMaximumNumber( List&lt;Integer&gt; numbers ) {return numbers.stream().reduce(Integer.MIN_VALUE, (x,y) -&gt; x &gt; y ? x : y );}// 최소 값 가져오기private static int afterMinimumNumber( List&lt;Integer&gt; numbers ) {return numbers.stream().reduce(Integer.MAX_VALUE, (x,y) -&gt; x &gt; y ? y : x );}// 각 수의 자신의 제곱 합private static int afterSquaredMethod( List&lt;Integer&gt; numbers ) {return numbers.stream().map(x -&gt; x*x).reduce(0, Integer::sum);}// 홀수 합private static int afterSumOfOddNumbers( List&lt;Integer&gt; numbers ) {return numbers.stream().filter(x -&gt; x%2 == 1 ).reduce(0, Integer::sum);}// 짝 합private static int afterSumOfEvenNumbers( List&lt;Integer&gt; numbers ) {return numbers.stream().filter(x -&gt; x%2 == 0 ).reduce(0, Integer::sum);}// 중복 제거private static void afteraaaaaaa (List&lt;Integer&gt; numbers) {numbers.stream().distinct().forEach(System.out::println);}// 숫자 정렬private static void afteraaaaaaab (List&lt;Integer&gt; numbers) {// 중복 허용 정렬numbers.stream().sorted().forEach(System.out::println);// 정렬시 중복 제거numbers.stream().distinct().sorted().forEach(System.out::println);}// 오른 차순 정렬private static void afterSortInAsc (List&lt;Integer&gt; numbers) {numbers.stream().distinct().sorted(Comparator.naturalOrder()).forEach(System.out::println);}// 내람 차순 정렬private static void afterSortInDesc (List&lt;Integer&gt; numbers) {numbers.stream().distinct().sorted(Comparator.reverseOrder()).forEach(System.out::println);}}</pre></div></div>

Stories by 신상훈 on Medium

Java Stream
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
public class StreamTest2 {
public static void main(String[] args) {
// jdk 1.9 이상 일경우 List.of 사용
// List<Integer> numbers = List.of(1,2,3,4,5,6,7);
List<Integer> numbers = Arrays.asList(15,1,2);
int sum = beforeAddListStructured(numbers);
System.out.println(sum);
int sumStream = afterAddListStructured(numbers);
System.out.println(sumStream);
afterSquaredMethod(numbers);
afterSortInAsc(numbers);
afterSortInDesc(numbers);
}
private static int beforeAddListStructured(List<Integer> numbers ) {
int sum = 0;
for (int number : numbers) {
sum += number;
}
return sum;
}
// 두개의 파람을 더하는 메소드
private static int sum(int aggregate , int nextNumber) {
return aggregate + nextNumber;
}
// 합계
private static int afterAddListStructured(List<Integer> numbers ) {
// reduce(초기값, 로직)
return numbers.stream()
// .reduce(0,StreamTest2::sum);
// .reduce(0, (x,y) -> x + y);
.reduce(0, Integer::sum);
}
// 시작 숫자 가저오기
private static int afterStartNumber( List<Integer> numbers ) {
return numbers.stream().reduce(0, (x,y) -> x );
}
// 마지막 숫자 가져오기
private static int afterLastNumber( List<Integer> numbers ) {
return numbers.stream().reduce(0, (x,y) -> y );
}
// 최대 값 가저오기
private static int afterMaximumNumber( List<Integer> numbers ) {
return numbers.stream().reduce(Integer.MIN_VALUE, (x,y) -> x > y ? x : y );
}
// 최소 값 가져오기
private static int afterMinimumNumber( List<Integer> numbers ) {
return numbers.stream().reduce(Integer.MAX_VALUE, (x,y) -> x > y ? y : x );
}
// 각 수의 자신의 제곱 합
private static int afterSquaredMethod( List<Integer> numbers ) {
return numbers.stream().map(x -> x*x).reduce(0, Integer::sum);
}
// 홀수 합
private static int afterSumOfOddNumbers( List<Integer> numbers ) {
return numbers.stream().filter(x -> x%2 == 1 ).reduce(0, Integer::sum);
}
// 짝 합
private static int afterSumOfEvenNumbers( List<Integer> numbers ) {
return numbers.stream().filter(x -> x%2 == 0 ).reduce(0, Integer::sum);
}
// 중복 제거
private static void afteraaaaaaa (List<Integer> numbers) {
numbers.stream().distinct().forEach(System.out::println);
}
// 숫자 정렬
private static void afteraaaaaaab (List<Integer> numbers) {
// 중복 허용 정렬
numbers.stream().sorted().forEach(System.out::println);
// 정렬시 중복 제거
numbers.stream().distinct().sorted().forEach(System.out::println);
}
// 오른 차순 정렬
private static void afterSortInAsc (List<Integer> numbers) {
numbers.stream().distinct().sorted(Comparator.naturalOrder()).forEach(System.out::println);
}
// 내람 차순 정렬
private static void afterSortInDesc (List<Integer> numbers) {
numbers.stream().distinct().sorted(Comparator.reverseOrder()).forEach(System.out::println);
}
}

Java stream - Step 02

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