20万毫安时充电宝能用多久 Java Variables

Ja Variables ❮ Previous Next ❯ Ja Variables

Variables are containers for storing data values.

In Ja, there are different types of variables, for example:

String - stores text, such as "Hello". String values are surrounded by double quotes int - stores integers (whole numbers), without decimals, such as 123 or -123 float - stores floating point numbers, with decimals, such as 19.99 or -19.99 char - stores single characters, such as 'a' or 'B'. Char values are surrounded by single quotes boolean - stores values with two states: true or false Declaring (Creating) Variables

To create a variable in Ja, you need to:

Choose a type (like int or String) Give the variable a name (like x, age, or name) Optionally assign it a value using =

Here's the basic syntax:

Syntax type variableName = value;

For example, if you want to store some text, you can use a String:

Example

Create a variable called name of type String and assign it the value "John". Then we use println() to print the name variable:

String name = "John"; System.out.println(name);

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To create a variable that should store a number, you can use int:

Example

Create a variable called myNum of type int and assign it the value 15:

int myNum = 15; System.out.println(myNum);

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You can also declare a variable without assigning the value, and assign the value later:

Example int myNum; myNum = 15; System.out.println(myNum);

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Note that if you assign a new value to an existing variable, it will overwrite the previous value:

Example

Change the value of myNum from 15 to 20:

int myNum = 15; myNum = 20; // myNum is now 20 System.out.println(myNum);

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Final Variables

If you don't want others (or yourself) to overwrite existing values, use the final keyword (this will declare the variable as "final" or "constant", which means unchangeable and read-only):

Example final int myNum = 15; myNum = 20; // will generate an error: cannot assign a value to a final variable

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Other Types

A demonstration of how to declare variables of other types:

Example int myNum = 5; float myFloatNum = 5.99f; char myLetter = 'D'; boolean myBool = true; String myText = "Hello";

You will learn more about data types in the next section.

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