The java.util.Arrays$ArrayList is a nested class inside the Arrays class. It is a fixed size or immutable list backed by an array. Arrays.java public static <T> List<T> asList(T… a) { return new ArrayList<>(a); } /** * @serial include */ private static class ArrayList<E> extends AbstractList<E> implements RandomAccess, java.io.Serializable { private static final long serialVersionUID = […]
In Java, we can use new ArrayList(Arrays.asList(array)) to convert an Array into an ArrayList ArrayExample1.java package com.mkyong; import java.util.ArrayList; import java.util.Arrays; import java.util.List; public class ArrayExample1 { public static void main(String[] args) { String[] str = {"A", "B", "C"}; List<String> list = new ArrayList<>(Arrays.asList(str)); list.add("D"); list.forEach(x -> System.out.println(x)); } } Output A B C D […]
A Java 2d array example. ArrayExample.java package com.mkyong; public class ArrayExample { public static void main(String[] args) { int[][] num2d = new int[2][3]; num2d[0][0] = 1; num2d[0][1] = 2; num2d[0][2] = 3; num2d[1][0] = 10; num2d[1][1] = 20; num2d[1][2] = 30; //or init 2d array like this : int[][] num2dInit = { {1, 2, 3}, […]
In JavaScript, we can use for, forEach or for..of to loop an Array. 1.1 for //old-school, classic for loop var str = ["a", "b", "c", "d", "e"]; for(var i =0; i < str.length; i++){ console.log(str[i]); //a,b,c,d,e } output a b c d e 1.2 forEach() var num = [1, 2, 3, 4, 5]; num.forEach(anyFunction) function […]
In JavaScript, we can use forEach(function) to loop an Array. The provided function in forEach() will run once for each array element. var total = 0; var num = [1, 2, 3, 4, 5]; num.forEach(anyFunction) function anyFunction(data){ total += data; } console.log(total); //15 var words = ""; var num = ["a", "b", "c", "d", "e"]; […]
In JavaScript, we can combine indexOf() and splice() to remove a certain element from an Array. var array = [1, 2, 3, 4, 5]; console.log(array) // I want remove num 4, find the index first, -1 if it is not present. var index = array.indexOf(4); if (index > -1) { // found array.splice(index, 1); } […]
In Java 8, we can use .toArray() to convert a Stream into an Array. 1. Stream -> String[] StreamString.java package com.mkyong; import java.util.Arrays; public class StreamString { public static void main(String[] args) { String lines = "I Love Java 8 Stream!"; // split by space, uppercase, and convert to Array String[] result = Arrays.stream(lines.split("\\s+")) .map(String::toUpperCase) […]
The key is boxed() the IntStream into a Stream<Integer>, then only convert to an Array. StreamExample.java package com.mkyong; import java.util.Arrays; import java.util.stream.IntStream; import java.util.stream.Stream; public class StreamExample { public static void main(String[] args) { //int[] -> IntStream -> Stream<Integer> -> Integer[] int[] num = {3, 4, 5}; //1. int[] -> IntStream IntStream stream = Arrays.stream(num); […]
Few Java examples to declare, initialize and manipulate Array in Java 1. Declares Array 1.1 For primitive types. ArrayExample1.java package com.mkyong; import java.util.Arrays; public class ArrayExample1 { public static void main(String[] args) { //declares an array of integers int[] num1 = new int[5]; int[] num2 = {1, 2, 3, 4, 5}; int[] num3 = new […]
This java.lang.ArrayIndexOutOfBoundsException is thrown when we are accessing an array with an index which is greater than the size of an array. P.S Array index starts with 0 ArrayExample.java package com.mkyong; public class ArrayExample { public static void main(String[] args) { // array of 3 int[] num = new int[3]; num[0] = 1; num[1] = […]
In JavaScript, you can use JSON.stringify to convert an array or values into a JSON formatted string. var output = {} output[0] = "a"; output[1] = "b"; output[2] = "c"; console.log( JSON.stringify(output) ); Output { "0":"a", "1":"b", "2":"c" } 1. jQuery Ajax Request Often times, you need to convert the JavaScript values into JSON before […]
The methods described below are only applicable to one dimensional arrays. Before we talk about the different ways to copy an array in Java we will show you how NOT to copy an Array. How NOT to copy an Array in Java Arrays in Java are Objects. If you try to treat them as variables… […]
Java examples to check if an Array (String or Primitive type) contains a certain values, updated with Java 8 stream APIs. 1. String Arrays 1.1 Check if a String Array contains a certain value “A”. StringArrayExample1.java package com.mkyong.core; import java.util.Arrays; import java.util.List; public class StringArrayExample1 { public static void main(String[] args) { String[] alphabet = […]
Code snippets to convert a primitive array int[] to a List<Integer> : int[] number = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}; List<Integer> list = new ArrayList<>(); for (int i : number) { list.add(i); } In Java 8, you can use the Stream APIs to do the boxing and conversion like this […]
In Java 8, you can either use Arrays.stream or Stream.of to convert an Array into a Stream. 1. Object Arrays For object arrays, both Arrays.stream and Stream.of returns the same output. TestJava8.java package com.mkyong.java8; import java.util.Arrays; import java.util.stream.Stream; public class TestJava8 { public static void main(String[] args) { String[] array = {"a", "b", "c", "d", […]
In this article, we will show you a few ways to join a Java Array. Apache Commons Lang – ArrayUtils Java API Java 8 Stream 1. Apache Commons Lang – ArrayUtils The simplest way is add the Apache Commons Lang library, and use ArrayUtils. addAll to join arrays. This method supports both primitive and object […]
In this article, we will show you a few ways to print a Java Array. Table of contents. 1. JDK 1.5 Arrays.toString 2. Java 8 Stream APIs 3. Java 8 Stream APIs – Collectors.joining 4. Jackson APIs 5. References 1. JDK 1.5 Arrays.toString We can use Arrays.toString to print a simple array and Arrays.deepToString for […]
This MongoDB article shows you how to remove a field from document and array. 1. Remove a field from Documents Sample of document, and you want to remove the field “affLink”. domain.json { “_id” : 1, “domain” : “mkyong.com”, “affLink” : “abc” } To remove a field from all documents, set {multi: true}, else only […]
Prior to MongoDB 2.6, there is no official function to $unset a field from array document. Note $unset is not working with arrays $pull is used to remove the entire record, not a particular field. 1. Arrays Documents In this article, we will show you how to remove the field “countryName” from below array. > […]
Java example to show the use of Arrays.sort() to sort an Array. The code should be self-explanatory. import java.util.Arrays; import java.util.Collections; public class ArraySorting{ public static void main(String args[]){ String[] unsortStringArray = new String[] {"c", "b", "a", "3", "2", "1"}; int[] unsortIntArray = new int[] {7,5,4,6,1,2,3}; System.out.println("Before sort"); System.out.println("— unsortStringArray —"); for(String temp: unsortStringArray){ System.out.println(temp); […]
Java example to show you how to convert a Array to a List ArrayToList.java package com.mkyong; import java.util.ArrayList; import java.util.Arrays; import java.util.List; import java.util.stream.Collectors; public class ArrayToList { public static void main(String[] argv) { String sArray[] = new String[] { "A", "B", "C" }; // convert array to list #1 List<String> list = Arrays.asList(sArray); System.out.println(list); […]
This article shows a few ways to detect if an array contains a duplicated value. Java 8 Stream, compare the array size. TreeSet, compare the array size. Two for loops, classic algorithm, 0(n^2). Set, 0(n). Bitmap, boolean[] 0(n). All the above solutions are tested with the below program and generate the same output. (except 5. […]
