Copy edits for Java arrays article (#20615)
* Copy edits for arrays Settling on British -ise endings rather than -ize, but either way works for me. * markdownize link americanize grammer fix inline code blocks to use single ticks turn output into code blocks to align with rest of articlepull/34185/head
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@ -4,34 +4,33 @@ title: Arrays
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# Array
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An Array is a collection of values (or objects) of similar datatypes (primitive and reference both form of datatypes are allowed) held in sequencial memory addresses.
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An Array is used to store a collection of similar data types.
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Arrays always start with the index of 0 and are instantiated to a set number of indexes.
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An Array is a collection of values (or objects) of similar data types (primitive and reference, both form of data types are allowed) held in sequential memory addresses.
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All the variables in the array must be of the same type, declared at instantiation.
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Arrays always start with the index of 0 and are instantiated to a set number of indexes.
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**Syntax:**
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```java
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dataType[] arrayName; // preferred way
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```
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Here, ```java datatype[] ``` describes that all the variables stated after it will be instantiated as arrays of the specified datatype. So, if we want to instantiate more arrays of the similar datatype, we just have to add them after the specified ```java arrayName```(Don't forget to separate them through commas only). An example is given below in the next section for reference.
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Here, `datatype[]` describes that all the variables stated after it will be instantiated as arrays of the specified datatype. So, if we want to instantiate more arrays of the similar datatype, we just have to add them after the specified `arrayName`(don't forget to separate them through commas only). An example is given below in the next section for reference.
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```java
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dataType arrayName[]; // works but not preferred way
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```
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Here, ```java datatype``` describes only that the variables stated after it belong to that datatype. Besides, ```java []``` after the variable name describes that the variable is an array of the specified datatype (not just a value or object of that datatype). So, if we want to instantiate more arrays of the similar datatype, we will add the variables names just after the one already specified, separated by commas and each time we will have to add ```java []``` after the variable name otherwise the variable will be instantiated as an ordinary value-storing variable (not an array). For better understanding an example is given in the next section.
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Here, `datatype` describes only that the variables stated after it belong to that datatype. Besides, `[]` after the variable name describes that the variable is an array of the specified datatype (not just a value or object of that datatype). So, if we want to instantiate more arrays of the similar datatype, we will add the variables names just after the one already specified, separated by commas and each time we will have to add `[]` after the variable name otherwise the variable will be instantiated as an ordinary value-storing variable (not an array). For better understanding an example is given in the next section.
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## Code snippets of above syntax:
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```java
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double[] list1, list2; // preferred way
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```
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Above code snippet instantiates 2 arrays of double type names list1 and list2.
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Above code snippet instantiates 2 arrays of double type named list1 and list2.
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```java
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double list1[], list2; // works but not preferred way
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```
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Above code snippet an array of datatype double named list1 and a simple variable of datatype double named list2 (Don't be confused with the name **list2**. Variables names have nothing to do with the type of variable).
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Above code snippet an array of datatype double named list1 and a simple variable of datatype double named list2 (Don't be confused by the name **list2**. Variables names have nothing to do with the type of variable).
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Note: The style `double list[]` is not preferred as it comes from the C/C++ language and was adopted in Java to accommodate C/C++ programmers. Additionally it's more readable: you can read that it's a "double array named list" other than "a double called list that is an array"
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Note: The style `double list[]` is not preferred as it comes from the C/C++ language and was adopted in Java to accommodate C/C++ programmers. Additionally it's more readable to use the style `double[] list`: you can easily read that it's a "double array named list" other than "a double called list that is an array."
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## Creating Arrays:
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double[] List = new double[10];
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```
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## Another way to create an Array:
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## Another way to declare and initialize an Array:
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```java
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dataType[] arrayName = {value_0, value_1, ..., value_k};
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arrayName[index] = value;
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```
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Note: You cannot change the size or type of an array after initialising it.
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Note: You cannot change the size or type of an array after initializing it.
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Note: You can however reset the array like so
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```java
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@ -101,7 +100,7 @@ arrayName = new dataType[] {value1, value2, value3};
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```
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## Size of Arrays:
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It's possible to find the number of elements in an array using the "length attribute". It should be noticed here that ```java length``` is an **attribute** of every array i.e. a variable name storing the length of the variable. It must not be confused for a **method** of array since the name is same as the ```java length()``` method corresponding to String classes.
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It's possible to find the number of elements in an array using the `length` attribute. It should be noted here that `length` is an **attribute** of every array, i.e., a variable storing the length of the array. It must not be confused for a **method** of Array since the name is same as the `length()` method corresponding to String classes.
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```java
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int[] a = {4, 5, 6, 7, 8}; // declare array
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System.out.println(a.length); //prints 5
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@ -144,23 +143,23 @@ for(int i = 0; i < M; i++) {
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}
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```
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This loop will execute M ^ N times and will build this:
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```java
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[ 0 | 1 | 2 | 3 | 4 ]
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[ 0 | 1 | 2 | 3 | 4 ]
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[ 0 | 1 | 2 | 3 | 4 ]
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[ 0 | 1 | 2 | 3 | 4 ]
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[ 0 | 1 | 2 | 3 | 4 ]
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```
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[ 0 | 1 | 2 | 3 | 4 ]
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[ 0 | 1 | 2 | 3 | 4 ]
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[ 0 | 1 | 2 | 3 | 4 ]
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[ 0 | 1 | 2 | 3 | 4 ]
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[ 0 | 1 | 2 | 3 | 4 ]
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Similarly a 3D array can also be made. It can be visualised as a cuboid instead of a rectangle(as above), divided into smaller cubes with each cube storing some value. It can be initialised follows:
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Similarly a 3D array can also be made. It can be visualized as a cuboid instead of a rectangle(as above), divided into smaller cubes with each cube storing some value. It can be initialized follows:
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```java
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int a=2, b=3, c=4;
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int[][][] a=new int[a][b][c];
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```
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In a similar manner, one can an array of as many dimensions as he/she wishes to but visualizing an array of more than 3 dimensions is difficult to visualize in a particular way.
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In a similar manner, one can declare an array of as many dimensions as desired, although visualizing an array of more than 3 dimensions is difficult.
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### Jagged Arrays
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Jagged arrays are multi-dimensional arrays that have a set number of rows but a varying number of columns. Jagged arrays are used to conserve memory use of the array. Here is a code example:
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Jagged arrays are multi-dimensional arrays that have a set number of rows but a varying number of columns. Jagged arrays are used to conserve memory use of the array. Here is an example:
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```java
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int[][] array = new int[5][]; //initialize a 2D array with 5 rows
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array[2] = new int[5]; //creates 5 columns for third row
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array[3] = new int[5]; //creates 5 columns for fourth row
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array[4] = new int[5]; //creates 5 columns for fifth row
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```
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```
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Output:
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```java
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[ 0 ]
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[ 0 | 1 ]
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[ 0 | 1 | 2 | 3 | 4 ]
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[ 0 | 1 | 2 | 3 | 4 ]
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[ 0 | 1 | 2 | 3 | 4 ]
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```
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#### More Information:
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* Source: <a href='https://docs.oracle.com/javase/tutorial/java/nutsandbolts/arrays.html' target='_blank' rel='nofollow'>Java Arrays</a>
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* Source: [Java Arrays](https://docs.oracle.com/javase/tutorial/java/nutsandbolts/arrays.html)
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