Java 8 streams

String s = "";
for (int i =0; i<100;i++){
	 s += "@" + (i <99 ? ", ":"");
}

String s = IntStream.range(0,100).mapToObj(n -> "@").collect(Collectors.joining(", "));

Edited by Iulius-Foyas, 08 May 2019 - 06:41.

_Smiley_, on 08 mai 2019 - 06:54, said:

public static String join(CharSequence delimiter, CharSequence... elements)

String[] arr = {"a","ab","abcdefghij", "abc", "abcdefg"};
String s = "";
for(int i = 0; i < arr.length; i++) {
	 if (arr[i].length() > s.length()) {
	 s = arr[i];
	 }
}

String[] arr = {"a","ab","abcdefghij", "abc", "abcdefg"};
String s = Arrays.asList(arr).stream().max(Comparator.comparing(n->n)).get();

Edited by Iulius-Foyas, 08 May 2019 - 07:12.

import java.io.IOException;
import java.util.stream.Collectors;
import java.util.stream.IntStream;

public class TestConcat {
	public static String testString() {
		String s = "";

		for (int i = 0; i <100; ++i) {
			s += "@" + (i < 99 ? ", " : "");
		}

		return s;
	}

	public static String testStream() {
		return IntStream.range(0,100).mapToObj(n -> "@").collect(Collectors.joining(", "));
	}

	public static String testStringBuilder() {
		StringBuilder sb = new StringBuilder();
		for (int i =0; i < 100; ++i) {
			sb.append("@").append(i < 99 ? ", " : "");
		}

		return sb.toString();
	}

	public static void main(String[] args) throws IOException {
		long start = System.nanoTime();
		String result = testString();
		long diff = System.nanoTime() - start;
		System.out.println("String Join " + diff);

		start = System.nanoTime();
		result = testStream();
		diff = System.nanoTime() - start;
		System.out.println("Stream Join " + diff);

		start = System.nanoTime();
		result = testStringBuilder();
		diff = System.nanoTime() - start;
		System.out.println("StringBuidler Join " + diff);
	}
}

public static String testStringBuilder() {
	StringBuilder sb = new StringBuilder();
	for (int i = 0; i < 99; ++i) {
		sb.append("@, ");
	}
	sb.append("@");

	return sb.toString();
}

Edited by DemocracySucks, 08 May 2019 - 08:32.

	public static String testStringBuilderWithIfTwoSeparators() {
		StringBuilder sb = new StringBuilder();

		for (int i =0; i < 100; ++i) {
			sb.append("@").append(i < 99 ? (i % 2 == 0 ? ", " : ". ") : "");
		}

		return sb.toString();
	}

Mosotti, on 08 mai 2019 - 07:23, said:

Edited by Iulius-Foyas, 08 May 2019 - 08:54.

Iulius-Foyas, on 08 mai 2019 - 08:50, said:

Iulius-Foyas, on 08 mai 2019 - 08:52, said:

Iulius-Foyas, on 08 mai 2019 - 06:40, said:

Mosotti, on 08 mai 2019 - 07:23, said:

d:\>java TestConcat
String Join 11842
Stream Join 10658
StringBuilder Join 15790
Array 5922
d:\>java TestConcat
String Join 11053
Stream Join 11052
StringBuilder Join 7500
Array 5921
d:\>java TestConcat
String Join 10658
Stream Join 10658
StringBuilder Join 16184
Array 7105
d:\>java TestConcat
String Join 10263
Stream Join 11447
StringBuilder Join 8685
Array 5921

d:\>java TestConcat
String Join 16599568
Stream Join 191054
StringBuilder Join 128290
Array 39474

Edited by dani.user, 08 May 2019 - 18:49.

Iulius-Foyas, on 08 mai 2019 - 07:08, said:

String[] arr = {"a","ab","abcdefghij", "abc", "abcdefg"};
String s = "";
for(int i = 0; i < arr.length; i++) {
	 if (arr[i].length() > s.length()) {
	 s = arr[i];
	 }
}

String[] arr = {"a","ab","abcdefghij", "abc", "abcdefg"};
String s = Arrays.asList(arr).stream().max(Comparator.comparing(n->n)).get();

val arr = Array("a", "ab", "abcdefghij", "abc", "abcdefg")
val longest : String = arr.maxBy(_.length)

dani.user, on 08 mai 2019 - 19:14, said:

val arr = Array("a", "ab", "abcdefghij", "abc", "abcdefg")
val longest : String = arr.maxBy(_.length)

def maxBy[B](f: A => B)(implicit cmp: Ordering[B]): A = {
if (isEmpty)
	 throw new UnsupportedOperationException("empty.maxBy")
var maxF: B = null.asInstanceOf[B]
var maxElem: A = null.asInstanceOf[A]
var first = true
for (elem <- self) {
	 val fx = f(elem)
	 if (first || cmp.gt(fx, maxF)) {
	 maxElem = elem
	 maxF = fx
	 first = false
	 }
}
maxElem
}

Edited by Iulius-Foyas, 08 May 2019 - 19:59.

dani.user, on 08 mai 2019 - 19:14, said:

dani.user, on 08 mai 2019 - 19:59, said:

Exercitiu mai avansat decat o simpla concatenare de siruri: Intr-un fisier csv avem date ca cele din poza. Sa se afiseze media pe clasa (9, 10, etc) a celor ce iau premiul 3.

elevi.png

Edited by Iulius-Foyas, 08 May 2019 - 20:09.

DemocracySucks, on 08 mai 2019 - 20:01, said:

DemocracySucks, on 08 mai 2019 - 20:01, said:

Iulius-Foyas, on 08 mai 2019 - 20:18, said:

Iulius-Foyas, on 08 mai 2019 - 20:18, said:

Iulius-Foyas, on 08 mai 2019 - 19:57, said: