Java程序设计实用教程 书中代码

例2-1

Example2_1.java

public class Example2_1 {

public static void main(String args[]) {

Rect rectangle1,rectangle2; //声明2个对象 rectangle1 = new Rect(); //创建对象 rectangle2 = new Rect(); rectangle1.width=128; rectangle1.height=69; rectangle2.width=18.9; rectangle2.height=59.8;

double area=rectangle1.getArea();

System.out.println(\的面积:\ area=rectangle2.getArea();

System.out.println(\的面积:\ } }

例2-2

Circle.java

public class Circle {

double radius; //圆的半径 double getArea() {

return 3.1415926*radius; } }

Lader.java

public class Lader {

double above; //梯形的上底 double bottom; //梯形的下底 double height; //梯形的高 double getArea() {

return (above+bottom)*height/2; } }

MainClass.java

public class MainClass

{

public static void main(String args[]) {

Circle circle=new Circle(); circle.radius=100;

double area=circle.getArea();

System.out.println(\圆的面积:\ Lader lader=new Lader(); lader.above=10; lader.bottom=56; lader.height=8.9; area=lader.getArea();

System.out.println(\梯形的面积:\ } }

例2-3

Rectangle.java

public class Rectangle //Rectangle类 {

double width; double height; double getArea() {

return width*height; } }

class Example2_3 //主类 {

public static void main(String args[]) {

Rectangle r; r=new Rectangle(); r.width=1.819; r.height=1.5;

double area=r.getArea();

System.out.println(\矩形的面积:\ } }

例2-4

Example2_4.java

public class Example2_4 {

public static void main (String args[ ])

{

char ch1='国',ch2='庆'; int p1=969,p2=12353;

System.out.println(ch1+\在Unicode表中的位置:\ System.out.println(ch2+\在Unicode表中的位置:\ System.out.println(\第\个位置上的字符是:\ System.out.println(\第\个位置上的字符是:\ } }

例2-5

People.java

public class People {

float weight; int height; void speak() {

System.out.println(\我的身高是:\ System.out.println(\我的体重是:\ } }

Machine.java

public class Machine {

public void estimate(int height,double weight) {

double number=(height-100)/weight; if(number>=1.1)

System.out.println(\偏瘦\ else if(number<1.1&&number>=0.96) System.out.println(\正常\ else if(number<0.96)

System.out.println(\偏胖\ } }

Example2_5.java

public class Example2_5 {

public static void main (String args[ ]) {

People 张三,李四; Machine 体检器; 体检器 = new Machine(); 张三 = new People(); 张三.weight=82.5F;

图2.8 判断胖瘦

张三.height=176; 张三.speak();

体检器.estimate(张三.height,张三.weight); 李四 = new People(); 李四.weight=77.2f; 李四.height=186; 李四.speak();

体检器.estimate(李四.height,李四.weight); } }

例2-6

Example2_6.java

import java.util.Scanner; public class Example2_6 {

public static void main(String args[]) {

Rect rectangle = new Rect(); Scanner reader = new Scanner(System.in);

System.out.println(\输入矩形的宽，并回车确认\ rectangle.width = reader.nextDouble();

System.out.println(\输入矩形的高，并回车确认\ rectangle.height = reader.nextDouble(); double area=rectangle.getArea();

System.out.println(\的面积:\ } }

图2.9 从命令行输入数据

例3-1

Number.java

public class Number { void sort(int a,int b,int c) { int count=0; int temp=0; if(b

System.out.println(\排序的第\次操作结果:\ } if(c

图3.6 排序整数

a=c; c=temp; count++;

System.out.println(\排序的第\次操作结果:\ } if(c

System.out.println(\排序的第\次操作结果:\ }

if(count==0) {

System.out.println(\排序的第\次操作结果:\ } } }

Example3_1.java

import java.util.Scanner; public class Example3_1 {

public static void main(String args[]) { Scanner reader = new Scanner(System.in);

System.out.println(\输入三个整数，每输入一个需回车确认\ int x = reader.nextInt(); int y = reader.nextInt(); int z = reader.nextInt();

Number number = new Number(); number.sort(x,y,z); } }

例3-2

Administrator.java

public class Administrator { void giveMess(int number) {

if(number/10000<=0||number/10000>=10) { System.out.println(\请给出5位数的彩票号码\ } else {

int d1 = number; // 尾号 int d2 = number0 ; // 后2位数 int d3 = number00 ;// 后3位数 switch(d1) { case 9 : case 3 :

case 1 : System.out.println(\彩票是三等奖\

图3.5 判断中奖

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