2_第2章Java语言基础.pptVIP

第二章 Java语言基础 ;Lecture 1 review;Lecture 1 review;Lecture 1 review;JDK Installation;JDK Installation;JDK Installation;2.1 标识符和保留字 ;2.2 数据类型 ;3.1 Java语言是强类型语言语言;3.2 简单数据类型;Primitive Type;3.3 整数类型;3.3.1 字节型（byte）;3.3.2 短整型（short）;3.3.3 整型（int）;3.3.4 长整型（long）;// Compute distance light travels using long variables. class Light { public static void main(String args[]) { int lightspeed; long days; long seconds; long distance; // approximate speed of light in miles per second lightspeed = 186000; days = 1000; // specify number of days here seconds = days * 24 * 60 * 60; // convert to seconds distance = lightspeed * seconds; // compute distance System.out.print(In + days); System.out.print( days light will travel about ); System.out.println(distance + miles.); } } ;Ans:;3.4 浮点型（Floating-Point Types）;3.4.1 单精度浮点型（float）;3.4.2 双精度型（double）浮点型;// Compute the area of a circle. class Area { public static void main(String args[]) { double pi，r，a; r = 10.8; // radius of circle pi = 3.1416; // pi，approximately a = pi * r * r; // compute area System.out.println(Area of circle is + a); } };3.5 字符;例;Ans:;// char variables behave like integers. class CharDemo2 { public static void main(String args[]) { char ch1; ch1 = X; System.out.println(ch1 contains + ch1); ch1++; // increment ch1,像整数一样进行运算操作 System.out.println(ch1 is now + ch1); } } ;Ans:;3.6 布尔型;// Demonstrate boolean values. class BoolTest { public static void main(String args[]) { boolean b; b = false; System.out.println(b is + b); b = true; System.out.println(b is + b); // a boolean value can control the if statement if(b) System.out.println(This is executed.); b = false; if(b) System.out.println(This is not executed.); // outcome of a relational operator is a boolean value System.out.println(10 9 is + (10 9)); } } ;Ans:;3.7 进一步研究自变量3.7.1 整数自变量;3.7.2 浮点