Tutorial by Examples



Basic cases int[] numbers1 = new int[3]; // Array for 3 int values, default value is 0 int[] numbers2 = { 1, 2, 3 }; // Array literal of 3 int values int[] numbers3 = new int[] { 1, 2, 3 }; // Array of 3 int values initialized int[][] numbers4 = { { 1, 2...
Two methods in java.util.Collection create an array from a collection: Object[] toArray() <T> T[] toArray(T[] a) Object[] toArray() can be used as follows: Java SE 5 Set<String> set = new HashSet<String>(); set.add("red"); set.add("blue"); ...
Java SE 5 Since Java 1.5 you can get a String representation of the contents of the specified array without iterating over its every element. Just use Arrays.toString(Object[]) or Arrays.deepToString(Object[]) for multidimentional arrays: int[] arr = {1, 2, 3, 4, 5}; System.out.println(Arrays.toS...
The Arrays.asList() method can be used to return a fixed-size List containing the elements of the given array. The resulting List will be of the same parameter type as the base type of the array. String[] stringArray = {"foo", "bar", "baz"}; List<String> stringL...
It is possible to define an array with more than one dimension. Instead of being accessed by providing a single index, a multidimensional array is accessed by specifying an index for each dimension. The declaration of multidimensional array can be done by adding [] for each dimension to a regular a...
The ArrayIndexOutOfBoundsException is thrown when a non-existing index of an array is being accessed. Arrays are zero-based indexed, so the index of the first element is 0 and the index of the last element is the array capacity minus 1 (i.e. array.length - 1). Therefore, any request for an array e...
Arrays are objects which provide space to store up to its size of elements of specified type. An array's size can not be modified after the array is created. int[] arr1 = new int[0]; int[] arr2 = new int[2]; int[] arr3 = new int[]{1, 2, 3, 4}; int[] arr4 = {1, 2, 3, 4, 5, 6, 7}; int len1 = ar...
Array types inherit their equals() (and hashCode()) implementations from java.lang.Object, so equals() will only return true when comparing against the exact same array object. To compare arrays for equality based on their values, use java.util.Arrays.equals, which is overloaded for all array types...
Java SE 8 Converting an array of objects to Stream: String[] arr = new String[] {"str1", "str2", "str3"}; Stream<String> stream = Arrays.stream(arr); Converting an array of primitives to Stream using Arrays.stream() will transform the array to a primitive sp...
You can iterate over arrays either by using enhanced for loop (aka foreach) or by using array indices: int[] array = new int[10]; // using indices: read and write for (int i = 0; i < array.length; i++) { array[i] = i; } Java SE 5 // extended for: read only for (int e : array) { ...
Java provides several ways to copy an array. for loop int[] a = { 4, 1, 3, 2 }; int[] b = new int[a.length]; for (int i = 0; i < a.length; i++) { b[i] = a[i]; } Note that using this option with an Object array instead of primitive array will fill the copy with reference to the origi...
Arrays are objects, but their type is defined by the type of the contained objects. Therefore, one cannot just cast A[] to T[], but each A member of the specific A[] must be cast to a T object. Generic example: public static <T, A> T[] castArray(T[] target, A[] array) { for (int i = 0; i...
Java doesn't provide a direct method in java.util.Arrays to remove an element from an array. To perform it, you can either copy the original array to a new one without the element to remove or convert your array to another structure allowing the removal. Using ArrayList You can convert the array t...
Object arrays are covariant, which means that just as Integer is a subclass of Number, Integer[] is a subclass of Number[]. This may seem intuitive, but can result in surprising behavior: Integer[] integerArray = {1, 2, 3}; Number[] numberArray = integerArray; // valid Number firstElement = numb...
The simple answer is that you cannot do this. Once an array has been created, its size cannot be changed. Instead, an array can only be "resized" by creating a new array with the appropriate size and copying the elements from the existing array to the new one. String[] listOfCities = ne...
There are many ways find the location of a value in an array. The following example snippets all assume that the array is one of the following: String[] strings = new String[] { "A", "B", "C" }; int[] ints = new int[] { 1, 2, 3, 4 }; In addition, each one sets...
Sorting arrays can be easily done with the Arrays api. import java.util.Arrays; // creating an array with integers int[] array = {7, 4, 2, 1, 19}; // this is the sorting part just one function ready to be used Arrays.sort(array); // prints [1, 2, 4, 7, 19] System.out.println(Arrays.toString...
Sometimes conversion of primitive types to boxed types is necessary. To convert the array, it's possible to use streams (in Java 8 and above): Java SE 8 int[] primitiveArray = {1, 2, 3, 4}; Integer[] boxedArray = Arrays.stream(primitiveArray).boxed().toArray(Integer[]::new); With lowe...

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