Java基础教程学习(一）基础结构

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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);    }}

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