Variables made easy

From WikiJava

The very first introduction to the Java variables. Simplest as should be.

the article

We could write the following simple code:

public class Interest1 { 
 
    public static void main (String[] args) {
 
        System.out.print("Interest after a year is:");
        System.out.println( 1234 * 0.025 );
    }
}

but no one could spot the meaning of that "magic numbers" 1234 and 0.025. A common way to improve the comprehension of the source is using the variables:

public class Interest2 { 
 
    public static void main (String[] args) {
 
        double interest;
        double capital;
        double tax = 0.025;
 
        capital = 1234;
        interest = capital * tax;
 
        System.out.print("Interest after a year is:");
        System.out.println(interest);
    }
}

'interest', 'capital' and 'tax' are all variables of type 'double'.

The Java syntax about variables:

<type> <name>;  // simple declaration
<type> <name1>, <name2>, ...;  // multiple declaration
 
// declaration with initialization
<type> <name> = <expression>;
<type> <name1> = <exp1>, <name2> = <exp2>, ...;

<type> could be a primitive type, a classe, an array type, ...

A primitive type could be:

• byte: integers between -128 and 127 (8 bit)
• short: integers between -32768 and 32767 (16 bit)
• int: integers between -2147483648 and 2147483647 (32 bit)
• long: integers (64 bit)
• float: floating point numbers (32 bit)
• double: floating point numbers (64 bit)
• char: characters (UNICODE standard, 16 bit)
• boolean: just two values: true or false

Comments from the users

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syntaxes to avoid

I'd like to point that the syntaxes:

<type> <name1>, <name2>, ...; 
<type> <name1> = <exp1>, <name2> = <exp2>, ...;

for defining multiple variables with a single command, should not be used because they make the code less legible. One variable per line is always to prefer.

Interesting though, thanks for sharing,

--DonGiulio 04:54, 21 June 2008 (PDT)