Sample Analysis of data types, variable Definitions and usage in JAVASE
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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