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This article mainly introduces the JAVASE data types, variable definition and the use of sample analysis, has a certain reference value, interested friends can refer to, I hope you can learn a lot after reading this article, the following let Xiaobian take you to understand.

A data type

Java is a strongly typed language, so data types should be distinguished and cannot be converted to each other after definition.

Two big data types of Java:

Built-in data type

Reference data type

The Java language provides eight basic types.

Two code examples:

Public class Test {

Static boolean bool

Static byte by

Static char ch

Static double d

Static float f

Static int i

Static long l

Static short sh

Static String str

Public static void main (String [] args) {

System.out.println ("Bool:" + bool)

System.out.println ("Byte:" + by)

System.out.println ("Character:" + ch)

System.out.println ("Double:" + d)

System.out.println ("Float:" + f)

System.out.println ("Integer:" + I)

System.out.println ("Long:" + l)

System.out.println ("Short:" + sh)

System.out.println ("String:" + str)

}

}

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Note that the long and float definitions are defined with L and f, respectively, for example:

Long a = 100000L

Float b = 234.5f

twelve

In fact, when defining double, we also need to write d, but in most cases we omit it.

Three reference types

In Java, a variable of a reference type is very similar to a pointer to Cstroke +. The reference type points to an object, and the variable pointing to the object is the reference variable. These variables are specified as a specific type when declared, such as Employee, Puppy, and so on. Once a variable is declared, the type cannot be changed.

Objects and arrays are reference data types. The default value for all reference types is null. A reference variable can be used to reference any type that is compatible with it.

Definition and use of four variables

Variable definition method: data type variable name = variable value; which is better to treat birthmarks in Zhengzhou http://www.zzzykdmlk.com/

For example:

Int age = 18

Use: direct output, or do operations, get, determine and compare. (personal understanding, it will improve the use after in-depth study.)

If (age > 17) {

Age=age+1

System.out.println (age)

}

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Naming rules of five variables

The first letter of the variable name must be the letter (amurz Amurz), the underscore (_), or the dollar sign ($). Avoid using spaces, Chinese characters, and keywords. Try to use hump nomenclature. Variable names are as meaningful as possible to avoid meaningless names such as: int a

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