Java基础教程学习(一）基础结构 - 变量，输入，输出

基础结构 - 变量，输入，输出
1.变量(Variables in Java)

The scalar types of Java
Java type	Allows for	Range of values
byte	very small integers	-128 to 127
short	small integers	-32768 to 32767
int	big integers	-2147483648 to 2147483647
long	very big integers	-9223372036854775808 to  9223372036854775807
float	real numbers	+/- 1.4 * 10-45 to 3.4 * 1038
double	very big real numbers	+/- 4.9 * 10-324 to 1.8 * 10308
char	characters	Unicode character set
boolean	true or false	not applicable

变量声明(declare) 
dataType variableName;
变量命名规则

不能是java中的关键字(void class)
名称中间不能有空格
不含有运算符和数字符合
创建常量(constant)

final int hours = 24;

2. 输出
    

System.out.println("hello");

3. 输入：Scanner类
 

Scanner专用类，获取来自键盘的信息

import java.util.Scanner;
public class Hello {
public static void main(String[] args){
Scanner sca = new Scanner(System.in);
double width, heiht,area;
System.out.println("***计算面积***");
System.out.print("输入宽的长度：");

width = sca.nextDouble();
System.out.print("输入高的大小：");
heiht = sca.nextDouble();
area = width*heiht;
System.out.print("面积为："+area);
}
}