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Vertex Academy

How to assign a value to a variable in java.

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The assigning of a value to a variable is carried out with the help of the "=" symbol.   Consider the following examples:

Example No.1

Let’s say we want to assign the value of "10" to the variable "k" of the "int" type. It’s very easy and can be done in two ways:

If you try to run this code on your computer, you will see the following:

In this example, we first declared the variable to be "k" of the "int" type:

Then in another line we assigned the value "10" to the variable "k":

As you you may have understood from the example, the "=" symbol is an assignment operation. It always works from right to left:

Variables Announement Vertex Academy

This assigns the value "10" to the variable "k."

As you can see, in this example we declared the variable as "k" of the int type and assigned the value to it in a single line:

int k = 10;

So, now you know that:

  • The "=" symbol is responsible for assignment operation and we assign values to variables with the help of this symbol.
  • There are two ways to assign a value to variables: in one line or in two lines.

What is variable initialization?

Actually, you already know what it is. Initialization is the assignment of an initial value to a variable. In other words, if you just created a variable and didn’t assign any value to it, then this variable is uninitialized. So, if you ever hear:

  • “We need to initialize the variable,” it simply means that “we need to assign the initial value to the variable.”
  • “The variable has been initialized,” it simply means that “we have assigned the initial value to the variable.”

Here's another example of variable initialization:

Example No.2

15 100 100000000 I love Java M 145.34567 3.14 true

In this line, we declared variable number1 of the byte type and, with the help of the "=" symbol, assigned the value 15 to it.

In this line, we declared variable number2 of the short type and, with the help of the "=" symbol, assigned the value 100 to it.

In this line, we declared variable number3 of the long type and, with the help of the "=" symbol, assigned the value 100000000 to it.

In this line, we declared the variable title of the string type and, with the help of the "=" symbol, assigned the value “I love Java” to it. Since this variable belongs to the string type, we wrote the value of the variable in double quotes .

In this line, we declared the variable letter of the char type and, with the help of the "=" symbol, assigned the value “M” to it. Note that since the variable belongs to the char type, we wrote the value of the variable in single quotes .

In this line, we declared the variable sum of the double type and, with the help of the "=" symbol, assigned the value "145.34567" to it.

In this line, we declared the variable pi of the float type and, with the help of the "=" symbol, assigned the value “3.14f” to it. Note that we added f to the number 3.14. This is a small detail that you'll need to remember: it's necessary to add f to the values of float variables.  However, when you see it in the console, it will show up as just 3.14 (without the "f").

In this line, we declared the variable result of the boolean type and, with the help of the "=" symbol, assigned the value "true" to it.

Then we display the values of all the variables in the console with the help of

LET’S SUMMARIZE:

  • We assign a value to a variable with the help of the assignment operator "=." It always works from right to left.

assign value to a variable Vertex Academy

2. There are two ways to assign a value to a variable:

  • in two lines
  • or in one line
  • You also need to remember:

If we assign a value to a variable of the string type, we need to put it in double quotes :

If we assign a value to a variable of the char type, we need to put it in single quotes :

If we assign a value to a variable of the float type, we need to  add the letter "f" :

  • "Initialization" means “to assign an initial value to a variable.”

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How to Declare and Initialize an Array in Java

declare assign java

  • Introduction

In this tutorial, we'll take a look at how to declare and initialize arrays in Java .

We declare an array in Java as we do other variables, by providing a type and name:

To initialize or instantiate an array as we declare it, meaning we assign values as when we create the array, we can use the following shorthand syntax:

Or, you could generate a stream of values and assign it back to the array:

To understand how this works, read more to learn the ins and outs of array declaration and instantiation!

  • Array Declaration in Java
  • Array Initialization in Java
  • IntStream.range()
  • IntStream.rangeClosed()
  • IntStream.of()
  • Java Array Loop Initialization

The declaration of an array object in Java follows the same logic as declaring a Java variable. We identify the data type of the array elements, and the name of the variable, while adding rectangular brackets [] to denote its an array.

Here are two valid ways to declare an array:

The second option is oftentimes preferred, as it more clearly denotes of which type intArray is.

Note that we've only created an array reference. No memory has been allocated to the array as the size is unknown, and we can't do much with it.

To use the array, we can initialize it with the new keyword, followed by the data type of our array, and rectangular brackets containing its size:

This allocates the memory for an array of size 10 . This size is immutable.

Java populates our array with default values depending on the element type - 0 for integers, false for booleans, null for objects, etc. Let's see more of how we can instantiate an array with values we want.

The slow way to initialize your array with non-default values is to assign values one by one:

In this case, you declared an integer array object containing 10 elements, so you can initialize each element using its index value.

The most common and convenient strategy is to declare and initialize the array simultaneously with curly brackets {} containing the elements of our array.

The following code initializes an integer array with three elements - 13, 14, and 15:

Keep in mind that the size of your array object will be the number of elements you specify inside the curly brackets. Therefore, that array object is of size three.

This method work for objects as well. If we wanted to initialize an array of three Strings, we would do it like this:

Java allows us to initialize the array using the new keyword as well:

It works the same way.

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Note : If you're creating a method that returns an initialized array, you will have to use the new keyword with the curly braces. When returning an array in a method, curly braces alone won't work:

If you're declaring and initializing an array of integers, you may opt to use the IntStream Java interface:

The above code creates an array of ten integers, containing the numbers 1 to 10:

The IntStream interface has a range() method that takes the beginning and the end of our sequence as parameters. Keep in mind that the second parameter is not included, while the first is.

We then use the method toArray() method to convert it to an array.

Note: IntStream is just one of few classes that can be used to create ranges. You can also use a DoubleStream or LongStream in any of these examples instead.

If you'd like to override that characteristic, and include the last element as well, you can use IntStream.rangeClosed() instead:

This produces an array of ten integers, from 1 to 10:

The IntStream.of() method functions very similarly to declaring an array with some set number of values, such as:

Here, we specify the elements in the of() call:

This produces an array with the order of elements preserved:

Or, you could even call the sorted() method on this, to sort the array as it's being initialized:

Which results in an array with this order of elements:

One of the most powerful techniques that you can use to initialize your array involves using a for loop to initialize it with some values.

Let's use a loop to initialize an integer array with values 0 to 9:

This is identical to any of the following, shorter options:

A loop is more ideal than the other methods when you have more complex logic to determine the value of the array element.

For example, with a for loop we can do things like making elements at even indices twice as large:

In this article, we discovered the different ways and methods you can follow to declare and initialize an array in Java. We've used curly braces {} , the new keyword and for loops to initialize arrays in Java, so that you have many options for different situations!

We've also covered a few ways to use the IntStream class to populate arrays with ranges of elements.

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Initialization, declaration and assignment terms in Java

A variable provides us with named storage that our programs can manipulate. Each variable in Java has a specific type, which determines the size and layout of the variable's memory; the range of values that can be stored within that memory; and the set of operations that can be applied to the variable.

You must declare all variables before they can be used. Following is the basic form of a variable declaration − data type variable [ = value][, variable [ = value] ...] ;

Here data type is one of Java's datatypes and variable is the name of the variable. To declare more than one variable of the specified type, you can use a comma-separated list.

Following are valid examples of variable declaration and initialization in Java −

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A variable is a container that holds values that are used in a Java program . To be able to use a variable it needs to be declared. Declaring variables is normally the first thing that happens in any program.

How to Declare a Variable

Java is a strongly typed programming language. This means that every variable must have a data type associated with it. For example, a variable could be declared to use one of the eight primitive data types : byte, short, int, long, float, double, char or boolean.

A good analogy for a variable is to think of a bucket. We can fill it to a certain level, we can replace what's inside it, and sometimes we can add or take something away from it. When we declare a variable to use a data type it's like putting a label on the bucket that says what it can be filled with. Let's say the label for the bucket is "Sand". Once the label is attached, we can only ever add or remove sand from the bucket. Anytime we try and put anything else into it, we will get stopped by the bucket police. In Java, you can think of the compiler as the bucket police. It ensures that programmers declare and use variables properly.

To declare a variable in Java, all that is needed is the data type followed by the variable name :

In the above example, a variable called "numberOfDays" has been declared with a data type of int. Notice how the line ends with a semi-colon. The semi-colon tells the Java compiler that the declaration is complete.

Now that it has been declared, numberOfDays can only ever hold values that match the definition of the data type (i.e., for an int data type the value can only be a whole number between -2,147,483,648 to 2,147,483,647).

Declaring variables for other data types is exactly the same:

Initializing Variables

Before a variable can be used it must be given an initial value. This is called initializing the variable. If we try to use a variable without first giving it a value:

To initialize a variable we use an assignment statement. An assignment statement follows the same pattern as an equation in mathematics (e.g., 2 + 2 = 4). There is a left side of the equation, a right side and an equals sign (i.e., "=") in the middle. To give a variable a value, the left side is the name of the variable and the right side is the value:

In the above example, numberOfDays has been declared with a data type of int and has been giving an initial value of 7. We can now add ten to the value of numberOfDays because it has been initialized:

Typically, the initializing of a variable is done at the same time as its declaration:

Choosing Variable Names

The name given to a variable is known as an identifier. As the term suggests, the way the compiler knows which variables it's dealing with is through the variable's name.

There are certain rules for identifiers:

  • reserved words cannot be used.
  • they cannot start with a digit but digits can be used after the first character (e.g., name1, n2ame are valid).
  • they can start with a letter, an underscore (i.e., "_") or a dollar sign (i.e., "$").
  • you cannot use other symbols or spaces (e.g., "%","^","&","#").

Always give your variables meaningful identifiers. If a variable holds the price of a book, then call it something like "bookPrice". If each variable has a name that makes it clear what it's being used for, it will make finding errors in your programs a lot easier.

Finally, there are naming conventions in Java that we would encourage you to use. You may have noticed that all the examples we have given follow a certain pattern. When more than one word is used in combination in a variable name the words following the first one are given a capital letter (e.g., reactionTime, numberOfDays.) This is known as mixed case and is the preferred choice for variable identifiers.

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An array with more than one dimension is known as a multi-dimensional array . The most commonly used multi-dimensional arrays are 2-D and 3-D arrays. We can say that any higher dimensional array is basically an array of arrays. A very common example of a 2D Array is Chess Board. A chessboard is a grid containing 64 1×1 square boxes. You can similarly visualize a 2D array. In a 2D array, every element is associated with a row number and column number. Accessing any element of the 2D array is similar to accessing the record of an Excel File using both row number and column number. 2D arrays are useful while implementing a Tic-Tac-Toe game, Chess, or even storing the image pixels. 

declare assign java

Declaring 2-D array in Java:

Any 2-dimensional array can be declared as follows:

data_type array_name[][];   (OR)     data_type[][] array_name;
  • data_type: Since Java is a statically-typed language (i.e. it expects its variables to be declared before they can be assigned values). So, specifying the datatype decides the type of elements it will accept. e.g. to store integer values only, the data type will be declared as int.
  • array_name: It is the name that is given to the 2-D array. e.g. subjects, students, fruits, department, etc.

Note: We can write [ ][ ] after data_type or we can write [ ][ ] after array_name while declaring the 2D array.

Different approaches for Initialization of 2-D array in Java:

data_type[][] array_Name = new data_type[no_of_rows][no_of_columns];

The total elements in any 2D array will be equal to (no_of_rows) * (no_of_columns).

  • no_of_rows: The number of rows in an array. e.g. no_of_rows = 3, then the array will have three rows.
  • no_of_columns: The number of columns in an array. e.g. no_of_columns = 4, then the array will have four columns.

The above syntax of array initialization will assign default values to all array elements according to the data type specified.  Below is the implementation of various approaches for initializing 2D arrays:

Approach 1:

Note: When you initialize a 2D array, you must always specify the first dimension(no. of rows), but providing the second dimension(no. of columns) may be omitted.

In the code snippet below, we have not specified the number of columns. However, the Java compiler is smart enough to manipulate the size by checking the number of elements inside the columns.

You can access any element of a 2D array using row numbers and column numbers.

declare assign java

Approach 2:

In the code snippet below, we have not specified the number of rows and columns. However, the Java compiler is smart enough to manipulate the size by checking the number of elements inside the rows and columns.

Approach 3:

Moreover, we can initialize each element of the array separately. Look at the code snippet below:

Using the above approach for array initialization would be a tedious task if the size of the 2D array is too large. The efficient way is to use for loop for initializing the array elements in the case of a large 2D array. 

Note: We can use arr. length function to find the size of the rows (1st dimension), and arr[0].length function to find the size of the columns (2nd dimension).

Approach 5: (Jagged arrays)

There may be a certain scenario where you want every row to have a different number of columns. This type of array is called a Jagged Array .

Program to add two 2D arrays:

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There are shortcuts in Java that let you type a little less code without introducing any new control structures.

Declaring and Assigning Variables You can declare multiple variables of the same type in one line of code:

You can also assign multiple variables to one value:

This code will set c to 5 and then set b to the value of c and finally a to the value of b .

Changing a variable One of the most common operations in Java is to assign a new value to a variable based on its current value. For example:

Since this is so common, Java let's you shorten it with a combined += operator that lets you skip the variable repetition:

(Note: Do not confuse this with index =+ 1; which would just assign positive 1 to index .)

In fact, any of the arithmetic operators can be used in this way:

j started at 3 and ended up at 5 after the above operations.

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Java Tutorial

Java methods, java classes, java file handling, java how to, java reference, java examples, java arrays.

Arrays are used to store multiple values in a single variable, instead of declaring separate variables for each value.

To declare an array, define the variable type with square brackets :

We have now declared a variable that holds an array of strings. To insert values to it, you can place the values in a comma-separated list, inside curly braces:

To create an array of integers, you could write:

Access the Elements of an Array

You can access an array element by referring to the index number.

This statement accesses the value of the first element in cars:

Try it Yourself »

Note: Array indexes start with 0: [0] is the first element. [1] is the second element, etc.

Change an Array Element

To change the value of a specific element, refer to the index number:

Array Length

To find out how many elements an array has, use the length property:

Test Yourself With Exercises

Create an array of type String called cars .

Start the Exercise

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  1. Java Variables

    Declaring (Creating) Variables To create a variable, you must specify the type and assign it a value: Syntax type variableName = value; Where type is one of Java's types (such as int or String ), and variableName is the name of the variable (such as x or name ). The equal sign is used to assign values to the variable.

  2. Java: define terms initialization, declaration and assignment

    11. Declaration is not to declare "value" to a variable; it's to declare the type of the variable. Assignment is simply the storing of a value to a variable. Initialization is the assignment of a value to a variable at the time of declaration. These definitions also applies to fields. int i; // simple declaration. i = 42 // simple assignment.

  3. Java Variable Declaration

    There are two ways to declare a variable in Java. The first method is to assign the initial value to the variable. The second method declares variable without initial value. Declare a Variable with Initial Value Data_type variable_name = value; For example: String my_name = "Java coder";

  4. How to Assign a Value to a Variable in Java • Vertex Academy

    It's very easy and can be done in two ways: Way No.1 1 2 3 4 5 6 7 class Test { public static void main(String args[]){ int k; k = 10; System.out.println (k); } } If you try to run this code on your computer, you will see the following: 10 In this example, we first declared the variable to be "k" of the "int" type: int k;

  5. A Guide to Java Initialization

    In Java, an initializer is a block of code that has no associated name or data type and is placed outside of any method, constructor, or another block of code. Java offers two types of initializers, static and instance initializers. Let's see how we can use each of them. 7.1. Instance Initializers.

  6. How to Declare and Initialize an Array in Java

    To initialize or instantiate an array as we declare it, meaning we assign values as when we create the array, we can use the following shorthand syntax: int [] myArray = { 13, 14, 15 }; Or, you could generate a stream of values and assign it back to the array: int [] intArray = IntStream.range( 1, 11 ).toArray();

  7. Initialization, declaration and assignment terms in Java

    Initialization declaration and assignment terms in Java - A variable provides us with named storage that our programs can manipulate. Each variable in Java has a specific type, which determines the size and layout of the variable's memory; the range of values that can be stored within that memory; and the set of operations that can be applied to the variab

  8. Java Variables: Declaration, Scope, and Naming Conventions

    Java Variable Declaration: Syntax and Best Practices. In Java, you can declare a variable using the following syntax: data_type variable_name = value; Here value is optional because in java, you can declare the variable first and then later assign the value to it. Here, data_type represents the type of data that the variable will hold, such as ...

  9. String Initialization in Java

    Finally, let's see how null Strings behave.. Let's declare and initialize a null String: String nullValue = null; If we printed nullValue, we'd see the word "null", as we previously saw.And, if we tried to invoke any methods on nullValue, we'd get a NullPointerException, as expected.. But, why does "null" is being printed?What is null actually?

  10. Java Variables

    How to Declare Variables in Java? We can declare variables in Java as pictorially depicted below as a visual aid. From the image, it can be easily perceived that while declaring a variable, we need to take care of two things that are: datatype: Type of data that can be stored in this variable. data_name: Name was given to the variable.

  11. Initialize a HashMap in Java

    As we can see, there's a huge improvement in this field since Java 9. As always, the sample source code is located in the Github project . The Java 9 examples are located here , and the Guava sample here .

  12. Tips for Declaring Variables in Java

    To declare a variable in Java, all that is needed is the data type followed by the variable name : In the above example, a variable called "numberOfDays" has been declared with a data type of int. Notice how the line ends with a semi-colon. The semi-colon tells the Java compiler that the declaration is complete.

  13. Java Declare Multiple Variables

    To declare more than one variable of the same type, you can use a comma-separated list: Example Get your own Java Server Instead of writing: int x = 5; int y = 6; int z = 50; System.out.println(x + y + z); You can simply write: int x = 5, y = 6, z = 50; System.out.println(x + y + z); Try it Yourself »

  14. Initializing multiple variables to the same value in Java

    76. You can declare multiple variables, and initialize multiple variables, but not both at the same time: String one,two,three; one = two = three = ""; However, this kind of thing (especially the multiple assignments) would be frowned upon by most Java developers, who would consider it the opposite of "visually simple". Share.

  15. Arrays in Java

    The general form of a one-dimensional array declaration is -- type var-name []; -- type [] var-name; An array declaration has two components: the type and the name. type declares the element type of the array. The element type determines the data type of each element that comprises the array.

  16. Different Ways To Declare And Initialize 2-D Array in Java

    Different Ways To Declare And Initialize 2-D Array in Java Read Practice An array with more than one dimension is known as a multi-dimensional array. The most commonly used multi-dimensional arrays are 2-D and 3-D arrays. We can say that any higher dimensional array is basically an array of arrays.

  17. Java Assignment Shortcuts

    There are shortcuts in Java that let you type a little less code without introducing any new control structures. Declaring and Assigning Variables. You can declare multiple variables of the same type in one line of code: int a, b, c; You can also assign multiple variables to one value: a = b = c = 5; This code will set c to 5 and then set b to ...

  18. What is the correct way to declare a boolean variable in Java?

    Ask Question Asked 11 years, 4 months ago Modified 7 years, 6 months ago Viewed 227k times 18 I have just started learning Java. In the online course I am following, I am asked to try the following code: String email1 = "[email protected]"; String email2 = "[email protected]"; Boolean isMatch = false; isMatch = email1.equals (email2); if (isMatch == true){

  19. Java Strings

    Create a variable of type String and assign it a value: String greeting = "Hello"; Try it Yourself » String Length A String in Java is actually an object, which contain methods that can perform certain operations on strings. For example, the length of a string can be found with the length () method: Example

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    Former President Donald Trump has a lead in the Republican presidential primary, but the process is far from over. The next step is South Carolina's primary, which takes place on Saturday ...

  21. How to directly initialize a HashMap (in a literal way)?

    With Java 8 or less. You can use static block to initialize a map with some values. Example : public static Map<String,String> test = new HashMap<String, String> static { test.put("test","test"); test.put("test1","test"); } With Java 9 or more. You can use Map.of() method to initialize a map with some values while declaring. Example :

  22. Java Arrays

    Java Arrays. Arrays are used to store multiple values in a single variable, instead of declaring separate variables for each value. To declare an array, define the variable type with square brackets: We have now declared a variable that holds an array of strings. To insert values to it, you can place the values in a comma-separated list, inside ...