From c3468b568799ca51e0a811e05f690396db78fd10 Mon Sep 17 00:00:00 2001 From: Akshay Ahuja Date: Wed, 25 Jun 2025 12:27:38 +0530 Subject: [PATCH 1/3] feat: Added jagged array documentation --- site/learn/language-basics/arrays/index.html | 576 +++++++++++++++++++ 1 file changed, 576 insertions(+) create mode 100644 site/learn/language-basics/arrays/index.html diff --git a/site/learn/language-basics/arrays/index.html b/site/learn/language-basics/arrays/index.html new file mode 100644 index 0000000..d9b9715 --- /dev/null +++ b/site/learn/language-basics/arrays/index.html @@ -0,0 +1,576 @@ + + + + + + + + + + + + + + +
+ + + +
+ +
+ + + +
+ + + + +
+ + + + + + + + + + + + + + + + + + +
+ + + + +
+ + +
+ +
+ Previous in the Series +
+
+ Creating Primitive Type Variables in Your Programs +
+
+ ➜ + + +
+
+ Current Tutorial +
+
Creating Arrays in Your Programs
+
+ + + ➜ +
+ That's the end of the series! +
+ + + +
+ + +
+ +

+ Previous in the Series: Creating Primitive Type Variables in Your Programs +

+ + + +
+ + + + +

Creating Arrays in Your Programs

+ + + +
+
+
+

 

+

Arrays

+

An array is a container object that holds a fixed number of values of a single type. The length of an array is established when the array is created. After creation, its length is fixed. You have seen an example of arrays already, in the main method of the "Hello World!" application. This section discusses arrays in greater detail.

+
+

+ An array of 8 elements. +

+
An array of 8 elements.
+
+ +

Each item in an array is called an element, and each element is accessed by its numerical index. As shown in the preceding illustration, numbering begins with 0. The 6th element, for example, would therefore be accessed at index 5.

+

The following program, ArrayDemo, creates an array of integers, puts some values in the array, and prints each value to standard output.

+
class ArrayDemo {
+    public static void main(String[] args) {
+        // declares an array of integers
+        int[] anArray;
+
+        // allocates memory for 10 integers
+        anArray = new int[10];
+
+        // initialize first element
+        anArray[0] = 100;
+        // initialize second element
+        anArray[1] = 200;
+        // and so forth
+        anArray[2] = 300;
+        anArray[3] = 400;
+        anArray[4] = 500;
+        anArray[5] = 600;
+        anArray[6] = 700;
+        anArray[7] = 800;
+        anArray[8] = 900;
+        anArray[9] = 1000;
+
+        System.out.println("Element at index 0: "
+                           + anArray[0]);
+        System.out.println("Element at index 1: "
+                           + anArray[1]);
+        System.out.println("Element at index 2: "
+                           + anArray[2]);
+        System.out.println("Element at index 3: "
+                           + anArray[3]);
+        System.out.println("Element at index 4: "
+                           + anArray[4]);
+        System.out.println("Element at index 5: "
+                           + anArray[5]);
+        System.out.println("Element at index 6: "
+                           + anArray[6]);
+        System.out.println("Element at index 7: "
+                           + anArray[7]);
+        System.out.println("Element at index 8: "
+                           + anArray[8]);
+        System.out.println("Element at index 9: "
+                           + anArray[9]);
+    }
+}
+
+

The output from this program is:

+
Element at index 0: 100
+Element at index 1: 200
+Element at index 2: 300
+Element at index 3: 400
+Element at index 4: 500
+Element at index 5: 600
+Element at index 6: 700
+Element at index 7: 800
+Element at index 8: 900
+Element at index 9: 1000
+
+

In a real-world programming situation, you would probably use one of the supported looping constructs to iterate through each element of the array, rather than write each line individually as in the preceding example. However, the example clearly illustrates the array syntax. You will learn about the various looping constructs (for, while, and do-while) in the Control Flow section.

+

 

+

Declaring a Variable to Refer to an Array

+

The preceding program declares an array (named anArray) with the following line of code:

+
// declares an array of integers
+int[] anArray;
+
+

Like declarations for variables of other types, an array declaration has two components: the array's type and the array's name. An array's type is written as type[], where type is the data type of the contained elements; the brackets are special symbols indicating that this variable holds an array. The size of the array is not part of its type (which is why the brackets are empty). An array's name can be anything you want, provided that it follows the rules and conventions as discussed in the Classes section. As with variables of other types, the declaration does not actually create an array; it simply tells the compiler that this variable will hold an array of the specified type.

+

Similarly, you can declare arrays of other types:

+
byte[] anArrayOfBytes;
+short[] anArrayOfShorts;
+long[] anArrayOfLongs;
+float[] anArrayOfFloats;
+double[] anArrayOfDoubles;
+boolean[] anArrayOfBooleans;
+char[] anArrayOfChars;
+String[] anArrayOfStrings;
+
+

You can also place the brackets after the array's name:

+
// this form is discouraged
+float anArrayOfFloats[];
+
+

However, convention discourages this form; the brackets identify the array type and should appear with the type designation.

+

 

+

Creating, Initializing, and Accessing an Array

+

One way to create an array is with the new operator. The next statement in the ArrayDemo program allocates an array with enough memory for 10 integer elements and assigns the array to the anArray variable.

+
// create an array of integers
+anArray = new int[10];
+
+

If this statement is missing, then the compiler prints an error like the following, and compilation fails:

+
ArrayDemo.java:4: Variable anArray may not have been initialized.
+
+

The next few lines assign values to each element of the array:

+
anArray[0] = 100; // initialize first element
+anArray[1] = 200; // initialize second element
+anArray[2] = 300; // and so forth
+
+

Each array element is accessed by its numerical index:

+
System.out.println("Element 1 at index 0: " + anArray[0]);
+System.out.println("Element 2 at index 1: " + anArray[1]);
+System.out.println("Element 3 at index 2: " + anArray[2]);
+
+

Alternatively, you can use the shortcut syntax to create and initialize an array:

+
int[] anArray = {
+    100, 200, 300,
+    400, 500, 600,
+    700, 800, 900, 1000
+};
+
+

Here the length of the array is determined by the number of values provided between braces and separated by commas.

+

You can also declare an array of arrays (also known as a multidimensional array) by using two or more sets of brackets, such as String[][] names. Each element, therefore, must be accessed by a corresponding number of index values.

+

In the Java programming language, a multidimensional array is an array whose components are themselves arrays. This is unlike arrays in C or Fortran. A consequence of this is that the rows are allowed to vary in length, as shown in the following MultiDimArrayDemo program:

+
class MultiDimArrayDemo {
+    public static void main(String[] args) {
+        String[][] names = {
+            {"Mr. ", "Mrs. ", "Ms. "},
+            {"Smith", "Jones"}
+        };
+        // Mr. Smith
+        System.out.println(names[0][0] + names[1][0]);
+        // Ms. Jones
+        System.out.println(names[0][2] + names[1][1]);
+    }
+}
+
+

The output from this program is:

+
Mr. Smith
+Ms. Jones
+
+

Working with Jagged Arrays

+

To create non-rectangular arrays (where inner arrays have different lengths), allocate each dimension separately:

+ 
// Declare outer array with fixed size
+int[][] jagged = new int[3][];
+
+// Initialize inner arrays with different lengths
+jagged[0] = new int[2];  // First row: 2 columns
+jagged[1] = new int[3];  // Second row: 3 columns
+jagged[2] = new int[1];  // Third row: 1 column
+
+// Assign values
+jagged[0][1] = 5;  // Row 0, Column 1
+jagged[1][2] = 9;  // Row 1, Column 2
+
+ +

Using the length Property

+

For multidimensional arrays, use the length property at each dimension:

+ 
System.out.println(jagged.length);     // 3 (outer array size)
+System.out.println(jagged[0].length);  // 2 (first inner array size)
+System.out.println(jagged[1].length);  // 3 (second inner array size)
+
+

Important: Accessing jagged[0][2] would throw ArrayIndexOutOfBoundsException since the first inner array only has indices 0-1.

+ +

Dynamic Initialization

+

Combine declaration and initialization for jagged arrays:

+ 
int[][] matrix = {
+    {1, 2},          // Row 0
+    {3, 4, 5},       // Row 1
+    {6, 7, 8, 9}     // Row 2
+};
+
+

Finally, you can use the built-in length property to determine the size of any array. The following code prints the array's size to standard output:

+
System.out.println(anArray.length);
+
+

 

+

Copying Arrays

+

The System class has an arraycopy() method that you can use to efficiently copy data from one array into another:

+
public static void arraycopy(Object src, int srcPos,
+                             Object dest, int destPos, int length)
+
+

The two Object arguments specify the array to copy from and the array to copy to. The three int arguments specify the starting position in the source array, the starting position in the destination array, and the number of array elements to copy.

+

The following program, ArrayCopyDemo, declares an array of String elements. It uses the System.arraycopy() method to copy a subsequence of array components into a second array:

+
class ArrayCopyDemo {
+    public static void main(String[] args) {
+        String[] copyFrom = {
+            "Affogato", "Americano", "Cappuccino", "Corretto", "Cortado",
+            "Doppio", "Espresso", "Frappucino", "Freddo", "Lungo", "Macchiato",
+            "Marocchino", "Ristretto" };
+
+        String[] copyTo = new String[7];
+        System.arraycopy(copyFrom, 2, copyTo, 0, 7);
+        for (String coffee : copyTo) {
+            System.out.print(coffee + " ");
+        }
+    }
+}
+
+

The output from this program is:

+
Cappuccino Corretto Cortado Doppio Espresso Frappucino Freddo
+
+

 

+

Array Manipulations

+

Arrays are a powerful and useful concept used in programming. Java SE provides methods to perform some of the most common manipulations related to arrays. For instance, the ArrayCopyDemo example uses the arraycopy() method of the System class instead of manually iterating through the elements of the source array and placing each one into the destination array. This is performed behind the scenes, enabling the developer to use just one line of code to call the method.

+

For your convenience, Java SE provides several methods for performing array manipulations (common tasks, such as copying, sorting and searching arrays) in the java.util.Arrays class. For instance, the previous example can be modified to use the java.util.Arrays method of the java.util.Arrays class, as you can see in the ArrayCopyOfDemo example. The difference is that using the java.util.Arrays method does not require you to create the destination array before calling the method, because the destination array is returned by the method:

+
class ArrayCopyOfDemo {
+    public static void main(String[] args) {
+        String[] copyFrom = {
+            "Affogato", "Americano", "Cappuccino", "Corretto", "Cortado",
+            "Doppio", "Espresso", "Frappucino", "Freddo", "Lungo", "Macchiato",
+            "Marocchino", "Ristretto" };
+
+        String[] copyTo = java.util.Arrays.copyOfRange(copyFrom, 2, 9);
+        for (String coffee : copyTo) {
+            System.out.print(coffee + " ");
+        }
+    }
+}
+
+

As you can see, the output from this program is the same, although it requires fewer lines of code. Note that the second parameter of the java.util.Arrays method is the initial index of the range to be copied, inclusively, while the third parameter is the final index of the range to be copied, exclusively. In this example, the range to be copied does not include the array element at index 9 (which contains the string Lungo).

+

Some other useful operations provided by methods in the java.util.Arrays class are:

+
    +
  • Searching an array for a specific value to get the index at which it is placed (the binarySearch() method).
    • +
  • Comparing two arrays to determine if they are equal or not (the equals() method).
    • +
  • Filling an array to place a specific value at each index (the fill() method).
    • +
  • Sorting an array into ascending order. This can be done either sequentially, using the sort() method, or concurrently, using the parallelSort() method introduced in Java SE 8. Parallel sorting of large arrays on multiprocessor systems is faster than sequential array sorting.
    • +
  • Creating a stream that uses an array as its source (the stream() method). For example, the following statement prints the contents of the copyTo array in the same way as in the previous example:
    • +
+
java.util.Arrays.stream(copyTo).map(coffee -> coffee + " ").forEach(System.out::print);
+
+

See Aggregate Operations for more information about streams.

+
    +
  • Converting an array to a string. The toString() method converts each element of the array to a string, separates them with commas, then surrounds them with brackets. For example, the following statement converts the copyTo array to a string and prints it:
    • +
+
System.out.println(java.util.Arrays.toString(copyTo));
+
+

This statement prints the following:

+
[Cappuccino, Corretto, Cortado, Doppio, Espresso, Frappucino, Freddo]
+
+

 

+

Wrapping-up Variables and Arrays

+

The Java programming language uses both "fields" and "variables" as part of its terminology. Instance variables (non-static fields) are unique to each instance of a class. Class variables (static fields) are fields declared with the static modifier; there is exactly one copy of a class variable, regardless of how many times the class has been instantiated. Local variables store temporary state inside a method. Parameters are variables that provide extra information to a method; both local variables and parameters are always classified as "variables" (not "fields"). When naming your fields or variables, there are rules and conventions that you should (or must) follow.

+

The eight primitive data types are: byte, short, int, long, float, double, boolean, and char. The java.lang.String class represents character strings. The compiler will assign a reasonable default value for fields of the above types; for local variables, a default value is never assigned.

+

A literal is the source code representation of a fixed value. An array is a container object that holds a fixed number of values of a single type. The length of an array is established when the array is created. After creation, its length is fixed.

+ + + +
+
+ + +
+ +
+ + +

Last update: August 27, 2022

+ + + +
+ + +
+ + +
+ +
+ Previous in the Series +
+
+ Creating Primitive Type Variables in Your Programs +
+
+ ➜ + + +
+
+ Current Tutorial +
+
Creating Arrays in Your Programs
+
+ + + ➜ +
+ That's the end of the series! +
+ + + +
+ + +
+ +

+ Previous in the Series: Creating Primitive Type Variables in Your Programs +

+ + + +
+ + + + + +
+ + +
+ + + + + + + + + + + + \ No newline at end of file From fb59c22c922ab306e857ccbf18b92348c7b39ef5 Mon Sep 17 00:00:00 2001 From: Akshay Ahuja Date: Wed, 25 Jun 2025 23:26:19 +0530 Subject: [PATCH 2/3] Removed incorrectly added HTML file and changed 03_creating-arrays.md --- site/learn/language-basics/arrays/index.html | 576 ------------------- 1 file changed, 576 deletions(-) delete mode 100644 site/learn/language-basics/arrays/index.html diff --git a/site/learn/language-basics/arrays/index.html b/site/learn/language-basics/arrays/index.html deleted file mode 100644 index d9b9715..0000000 --- a/site/learn/language-basics/arrays/index.html +++ /dev/null @@ -1,576 +0,0 @@ - - - - - - - - - - - - - - -
- - - -
- - - - - - -
- - - - - - - - - - - - - - - - - - -
- - - - -
- - -
- -
- Previous in the Series -
-
- Creating Primitive Type Variables in Your Programs -
-
- ➜ - - -
-
- Current Tutorial -
-
Creating Arrays in Your Programs
-
- - - ➜ -
- That's the end of the series! -
- - - -
- - -
- -

- Previous in the Series: Creating Primitive Type Variables in Your Programs -

- - - -
- - - - -

Creating Arrays in Your Programs

- - - -
-
-
-

 

-

Arrays

-

An array is a container object that holds a fixed number of values of a single type. The length of an array is established when the array is created. After creation, its length is fixed. You have seen an example of arrays already, in the main method of the "Hello World!" application. This section discusses arrays in greater detail.

-
-

- An array of 8 elements. -

-
An array of 8 elements.
-
- -

Each item in an array is called an element, and each element is accessed by its numerical index. As shown in the preceding illustration, numbering begins with 0. The 6th element, for example, would therefore be accessed at index 5.

-

The following program, ArrayDemo, creates an array of integers, puts some values in the array, and prints each value to standard output.

-
class ArrayDemo {
-    public static void main(String[] args) {
-        // declares an array of integers
-        int[] anArray;
-
-        // allocates memory for 10 integers
-        anArray = new int[10];
-
-        // initialize first element
-        anArray[0] = 100;
-        // initialize second element
-        anArray[1] = 200;
-        // and so forth
-        anArray[2] = 300;
-        anArray[3] = 400;
-        anArray[4] = 500;
-        anArray[5] = 600;
-        anArray[6] = 700;
-        anArray[7] = 800;
-        anArray[8] = 900;
-        anArray[9] = 1000;
-
-        System.out.println("Element at index 0: "
-                           + anArray[0]);
-        System.out.println("Element at index 1: "
-                           + anArray[1]);
-        System.out.println("Element at index 2: "
-                           + anArray[2]);
-        System.out.println("Element at index 3: "
-                           + anArray[3]);
-        System.out.println("Element at index 4: "
-                           + anArray[4]);
-        System.out.println("Element at index 5: "
-                           + anArray[5]);
-        System.out.println("Element at index 6: "
-                           + anArray[6]);
-        System.out.println("Element at index 7: "
-                           + anArray[7]);
-        System.out.println("Element at index 8: "
-                           + anArray[8]);
-        System.out.println("Element at index 9: "
-                           + anArray[9]);
-    }
-}
-
-

The output from this program is:

-
Element at index 0: 100
-Element at index 1: 200
-Element at index 2: 300
-Element at index 3: 400
-Element at index 4: 500
-Element at index 5: 600
-Element at index 6: 700
-Element at index 7: 800
-Element at index 8: 900
-Element at index 9: 1000
-
-

In a real-world programming situation, you would probably use one of the supported looping constructs to iterate through each element of the array, rather than write each line individually as in the preceding example. However, the example clearly illustrates the array syntax. You will learn about the various looping constructs (for, while, and do-while) in the Control Flow section.

-

 

-

Declaring a Variable to Refer to an Array

-

The preceding program declares an array (named anArray) with the following line of code:

-
// declares an array of integers
-int[] anArray;
-
-

Like declarations for variables of other types, an array declaration has two components: the array's type and the array's name. An array's type is written as type[], where type is the data type of the contained elements; the brackets are special symbols indicating that this variable holds an array. The size of the array is not part of its type (which is why the brackets are empty). An array's name can be anything you want, provided that it follows the rules and conventions as discussed in the Classes section. As with variables of other types, the declaration does not actually create an array; it simply tells the compiler that this variable will hold an array of the specified type.

-

Similarly, you can declare arrays of other types:

-
byte[] anArrayOfBytes;
-short[] anArrayOfShorts;
-long[] anArrayOfLongs;
-float[] anArrayOfFloats;
-double[] anArrayOfDoubles;
-boolean[] anArrayOfBooleans;
-char[] anArrayOfChars;
-String[] anArrayOfStrings;
-
-

You can also place the brackets after the array's name:

-
// this form is discouraged
-float anArrayOfFloats[];
-
-

However, convention discourages this form; the brackets identify the array type and should appear with the type designation.

-

 

-

Creating, Initializing, and Accessing an Array

-

One way to create an array is with the new operator. The next statement in the ArrayDemo program allocates an array with enough memory for 10 integer elements and assigns the array to the anArray variable.

-
// create an array of integers
-anArray = new int[10];
-
-

If this statement is missing, then the compiler prints an error like the following, and compilation fails:

-
ArrayDemo.java:4: Variable anArray may not have been initialized.
-
-

The next few lines assign values to each element of the array:

-
anArray[0] = 100; // initialize first element
-anArray[1] = 200; // initialize second element
-anArray[2] = 300; // and so forth
-
-

Each array element is accessed by its numerical index:

-
System.out.println("Element 1 at index 0: " + anArray[0]);
-System.out.println("Element 2 at index 1: " + anArray[1]);
-System.out.println("Element 3 at index 2: " + anArray[2]);
-
-

Alternatively, you can use the shortcut syntax to create and initialize an array:

-
int[] anArray = {
-    100, 200, 300,
-    400, 500, 600,
-    700, 800, 900, 1000
-};
-
-

Here the length of the array is determined by the number of values provided between braces and separated by commas.

-

You can also declare an array of arrays (also known as a multidimensional array) by using two or more sets of brackets, such as String[][] names. Each element, therefore, must be accessed by a corresponding number of index values.

-

In the Java programming language, a multidimensional array is an array whose components are themselves arrays. This is unlike arrays in C or Fortran. A consequence of this is that the rows are allowed to vary in length, as shown in the following MultiDimArrayDemo program:

-
class MultiDimArrayDemo {
-    public static void main(String[] args) {
-        String[][] names = {
-            {"Mr. ", "Mrs. ", "Ms. "},
-            {"Smith", "Jones"}
-        };
-        // Mr. Smith
-        System.out.println(names[0][0] + names[1][0]);
-        // Ms. Jones
-        System.out.println(names[0][2] + names[1][1]);
-    }
-}
-
-

The output from this program is:

-
Mr. Smith
-Ms. Jones
-
-

Working with Jagged Arrays

-

To create non-rectangular arrays (where inner arrays have different lengths), allocate each dimension separately:

- 
// Declare outer array with fixed size
-int[][] jagged = new int[3][];
-
-// Initialize inner arrays with different lengths
-jagged[0] = new int[2];  // First row: 2 columns
-jagged[1] = new int[3];  // Second row: 3 columns
-jagged[2] = new int[1];  // Third row: 1 column
-
-// Assign values
-jagged[0][1] = 5;  // Row 0, Column 1
-jagged[1][2] = 9;  // Row 1, Column 2
-
- -

Using the length Property

-

For multidimensional arrays, use the length property at each dimension:

- 
System.out.println(jagged.length);     // 3 (outer array size)
-System.out.println(jagged[0].length);  // 2 (first inner array size)
-System.out.println(jagged[1].length);  // 3 (second inner array size)
-
-

Important: Accessing jagged[0][2] would throw ArrayIndexOutOfBoundsException since the first inner array only has indices 0-1.

- -

Dynamic Initialization

-

Combine declaration and initialization for jagged arrays:

- 
int[][] matrix = {
-    {1, 2},          // Row 0
-    {3, 4, 5},       // Row 1
-    {6, 7, 8, 9}     // Row 2
-};
-
-

Finally, you can use the built-in length property to determine the size of any array. The following code prints the array's size to standard output:

-
System.out.println(anArray.length);
-
-

 

-

Copying Arrays

-

The System class has an arraycopy() method that you can use to efficiently copy data from one array into another:

-
public static void arraycopy(Object src, int srcPos,
-                             Object dest, int destPos, int length)
-
-

The two Object arguments specify the array to copy from and the array to copy to. The three int arguments specify the starting position in the source array, the starting position in the destination array, and the number of array elements to copy.

-

The following program, ArrayCopyDemo, declares an array of String elements. It uses the System.arraycopy() method to copy a subsequence of array components into a second array:

-
class ArrayCopyDemo {
-    public static void main(String[] args) {
-        String[] copyFrom = {
-            "Affogato", "Americano", "Cappuccino", "Corretto", "Cortado",
-            "Doppio", "Espresso", "Frappucino", "Freddo", "Lungo", "Macchiato",
-            "Marocchino", "Ristretto" };
-
-        String[] copyTo = new String[7];
-        System.arraycopy(copyFrom, 2, copyTo, 0, 7);
-        for (String coffee : copyTo) {
-            System.out.print(coffee + " ");
-        }
-    }
-}
-
-

The output from this program is:

-
Cappuccino Corretto Cortado Doppio Espresso Frappucino Freddo
-
-

 

-

Array Manipulations

-

Arrays are a powerful and useful concept used in programming. Java SE provides methods to perform some of the most common manipulations related to arrays. For instance, the ArrayCopyDemo example uses the arraycopy() method of the System class instead of manually iterating through the elements of the source array and placing each one into the destination array. This is performed behind the scenes, enabling the developer to use just one line of code to call the method.

-

For your convenience, Java SE provides several methods for performing array manipulations (common tasks, such as copying, sorting and searching arrays) in the java.util.Arrays class. For instance, the previous example can be modified to use the java.util.Arrays method of the java.util.Arrays class, as you can see in the ArrayCopyOfDemo example. The difference is that using the java.util.Arrays method does not require you to create the destination array before calling the method, because the destination array is returned by the method:

-
class ArrayCopyOfDemo {
-    public static void main(String[] args) {
-        String[] copyFrom = {
-            "Affogato", "Americano", "Cappuccino", "Corretto", "Cortado",
-            "Doppio", "Espresso", "Frappucino", "Freddo", "Lungo", "Macchiato",
-            "Marocchino", "Ristretto" };
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-        String[] copyTo = java.util.Arrays.copyOfRange(copyFrom, 2, 9);
-        for (String coffee : copyTo) {
-            System.out.print(coffee + " ");
-        }
-    }
-}
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As you can see, the output from this program is the same, although it requires fewer lines of code. Note that the second parameter of the java.util.Arrays method is the initial index of the range to be copied, inclusively, while the third parameter is the final index of the range to be copied, exclusively. In this example, the range to be copied does not include the array element at index 9 (which contains the string Lungo).

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Some other useful operations provided by methods in the java.util.Arrays class are:

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  • Searching an array for a specific value to get the index at which it is placed (the binarySearch() method).
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  • Comparing two arrays to determine if they are equal or not (the equals() method).
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  • Filling an array to place a specific value at each index (the fill() method).
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  • Sorting an array into ascending order. This can be done either sequentially, using the sort() method, or concurrently, using the parallelSort() method introduced in Java SE 8. Parallel sorting of large arrays on multiprocessor systems is faster than sequential array sorting.
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  • Creating a stream that uses an array as its source (the stream() method). For example, the following statement prints the contents of the copyTo array in the same way as in the previous example:
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java.util.Arrays.stream(copyTo).map(coffee -> coffee + " ").forEach(System.out::print);
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See Aggregate Operations for more information about streams.

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  • Converting an array to a string. The toString() method converts each element of the array to a string, separates them with commas, then surrounds them with brackets. For example, the following statement converts the copyTo array to a string and prints it:
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System.out.println(java.util.Arrays.toString(copyTo));
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This statement prints the following:

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[Cappuccino, Corretto, Cortado, Doppio, Espresso, Frappucino, Freddo]
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Wrapping-up Variables and Arrays

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The Java programming language uses both "fields" and "variables" as part of its terminology. Instance variables (non-static fields) are unique to each instance of a class. Class variables (static fields) are fields declared with the static modifier; there is exactly one copy of a class variable, regardless of how many times the class has been instantiated. Local variables store temporary state inside a method. Parameters are variables that provide extra information to a method; both local variables and parameters are always classified as "variables" (not "fields"). When naming your fields or variables, there are rules and conventions that you should (or must) follow.

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The eight primitive data types are: byte, short, int, long, float, double, boolean, and char. The java.lang.String class represents character strings. The compiler will assign a reasonable default value for fields of the above types; for local variables, a default value is never assigned.

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A literal is the source code representation of a fixed value. An array is a container object that holds a fixed number of values of a single type. The length of an array is established when the array is created. After creation, its length is fixed.

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Last update: August 27, 2022

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- - - - - - - - - - - - \ No newline at end of file From 09597d40b22e1dca1af64c7daa0e5cef20f37228 Mon Sep 17 00:00:00 2001 From: Akshay Ahuja Date: Wed, 25 Jun 2025 23:26:58 +0530 Subject: [PATCH 3/3] Added correct markdown file --- .../02_basics/03_creating-arrays.md | 58 +++++++++++++++++++ 1 file changed, 58 insertions(+) diff --git a/app/pages/learn/01_tutorial/03_getting-to-know-the-language/02_basics/03_creating-arrays.md b/app/pages/learn/01_tutorial/03_getting-to-know-the-language/02_basics/03_creating-arrays.md index 9cfea3a..fd2ff20 100644 --- a/app/pages/learn/01_tutorial/03_getting-to-know-the-language/02_basics/03_creating-arrays.md +++ b/app/pages/learn/01_tutorial/03_getting-to-know-the-language/02_basics/03_creating-arrays.md @@ -209,6 +209,64 @@ Mr. Smith Ms. Jones ``` +  +## Working with Jagged Arrays + +A **jagged array** (an array of arrays) in Java lets each row have a different length. For example, one row might have 3 elements while another has 2. To create a jagged array, first declare the outer array with a size but no specified inner lengths, then assign each sub-array its own size. + +--- + +## Step 1 – Declare the jagged array +```java +int[][] jaggedArray = new int[3][]; +``` + +## Step 2 – Initialize each row with different sizes or values +```java +jaggedArray[0] = new int[] {1, 2, 3}; +jaggedArray[1] = new int[] {4, 5}; +jaggedArray[2] = new int[] {6, 7, 8, 9}; +``` +Each assignment gives a different length (3, 2, and 4 elements respectively) for rows 0, 1, and 2. + +## Step 3 – Use nested loops to print all elements + +```java +System.out.println("Jagged array elements:"); +for (int i = 0; i < jaggedArray.length; i++) { + for (int j = 0; j < jaggedArray[i].length; j++) { + System.out.print(jaggedArray[i][j] + " "); + } + System.out.println(); +} +``` +This will print every element in the jagged array in row-major order. + +## Step 4 – Print array lengths +```java +System.out.println("Outer array length: " + jaggedArray.length); +for (int i = 0; i < jaggedArray.length; i++) { + System.out.println("Length of row " + i + ": " + jaggedArray[i].length); +} +``` +This outputs the size of the outer array and each inner row length, confirming the structure of the jagged array. + +### Output: +```java +Jagged array elements: +1 2 3 +4 5 +6 7 8 9 +Outer array length: 3 +Length of row 0: 3 +Length of row 1: 2 +Length of row 2: 4 + +``` + + + + Finally, you can use the built-in `length` property to determine the size of any array. The following code prints the array's size to standard output: ```java