JAVA语言程序设计清华大学书上例题源代码

1、2_1】/ 计算二个数的和 class Example2_1 public static void main(String args) int x,y,s;x = 3;y = 5; s =x+y; / 求和 System.out.println(" 二数之和为： " + s);2_2】/ 计算圆的面积 class Example2_2 public static void main(String args) double pi,r,s;r = 10.8; / 圆的半径 pi = 3.1416;s = pi * r * r; / 计算面积 System.out.println

2、(" 圆的面积为： " + s);2_3】/* char 变量的用法 */ class Example2_3 public static void main(String args) char ch1,ch2; ch1 = 88; / code for X ch2 = 'Y'System.out.print("ch1 and ch2 ： "); System.out.println(ch1 + " " + ch2);2_4】/* 布尔类型的用法 */ class Example2_4 public static voi

3、d main(String args) boolean b; b = false;System.out.println("b is " + b); b = true;System.out.println("b is " + b);/ outcome of a relational operator is a boolean valueSystem.out.println("10 > 9 is " + (10 > 9);【2_5】public class Example2_5public static void main(S

4、tring agrs)/ 定义几个变量并赋值int a=41;int b=21;double x=6.4;double y=3.22;System.out.println(" 变量数值： ");System.out.println("a="+a);System.out.println("b="+b);System.out.println("x="+x);System.out.println("y="+y);/ 加法System.out.println(" 加 :");Syst

5、em.out.println("a+b="+(a+b);System.out.println("x+y="+(x+y);/ 减法System.out.println(" 减 :");System.out.println("a-b="+(a-b); System.out.println("x-y="+(x-y);/ 乘法System.out.println(" 乘 :");System.out.println("a*b="+(a*b);System.out.

6、println("x*y="+(x*y);/ 除法System.out.println(" 除 :");System.out.println("a/b="+(a/b); System.out.println("x/y="+(x/y);/ 从除法中求得余数System.out.println(" 计算余数 :");System.out.println("a%b="+(a%b); System.out.println("x%y="+(x%y);/ 混合类型Sy

7、stem.out.println(" 混合类型 :");System.out.println("b+y="+(b+y); System.out.println("a*x="+(a*x);【2_6】public class Example2_6public static void main(String args)/ 定义若干整型数int i=37;int j=42;int k=42;System.out.println(" 变量数值 ");System.out.println("i="+i);S

8、ystem.out.println("j="+j);System.out.println("k="+k);/ 大于System.out.println(" 大于 :");System.out.println("i>j="+(i>j);/falseSystem.out.println("j>i="+(j>i);/trueSystem.out.println("k>j="+(k>j);/false/ 大于等于System.out.println

9、(" 大于等于 :");System.out.println("i>=j="+(i>=j);/falseSystem.out.println("j>=i="+(j>=i);/trueSystem.out.println("k>=j="+(k>=j);/true/ 小于System.out.println(" 小于 :");System.out.println("i<j="+(i<j);/trueSystem.out.printl

10、n("j<i="+(j<i);/falseSystem.out.println("k<j="+(k<j);/false/ 小于等于System.out.println(" 小于等于 :");System.out.println("i<=j="+(i<=j);/trueSystem.out.println("j<=i="+(j<=i);/falseSystem.out.println("k<=j="+(k<=j);/f

11、alse / 等于System.out.println(" 等于 :");System.out.println("i=j="+(i=j);/falseSystem.out.println("k=j="+(k=j);/true/ 不等于System.out.println(" 不等于 :");System.out.println("i!=j="+(i!=j);/trueSystem.out.println("k!=j="+(k!=j);/false【2_7】class Exam

12、ple2_7public static void main(String args)/ 字符char a仁'银',a2='行',a3='帐',a4='号'；/ 密鈅char secret='x'；/ 异或运算加密a1=(char)(a"secret);a2=(char)(a2Asecret);a3=(char)(a3Asecret);a4=(char)(a4Asecret);System.out.println(” 密文:"+a1+a2+a3+a4);/ 再一次异或运算解密a1=(char)(a

13、1Asecret);a2=(char)(a2Asecret);a3=(char)(a3Asecret);a4=(char)(a4Asecret);System.out.println(” 原文:"+a1+a2+a3+a4);【2_8】/* if 结构 */public class Example2_8public static void main(String args)int a=9,b=5,c=7,t;if(a>b)t=a; a=b; b=t;if(a>c)t=a; a=c; c=t;if(b>c)t=b; b=c; c=t;System.out.println

14、("a="+a+",b="+b+",c="+c);/* if-else-if 结构 . */2_9】class Example2_9 public static void main(String args) int month = 4; / 4 月份String season;if(month = 12 | month = 1 | month = 2)season = "冬天 "else if(month = 3 | month = 4 | month = 5) season = "春天 " e

15、lse if(month = 6 | month = 7 | month = 8) season = "夏天 " else if(month = 9 | month = 10 | month = 11)season = "秋天 " else season = "不合法的月份 " System.out.println("4 月是 " + season + ".");【2_10】/* switch 开关语句 */import java.applet.*;import java.awt.*;publi

16、c class Example2_10 extends Appletpublic void paint(Graphics g)int x=1,y=1;switch(x+y)case 1 : g.setColor(Color.red); g.drawString("i am 1",5,10); break;case 2: g.setColor(Color.blue); g.drawString("i am 2",5,10);/ break;case 3:g.setColor(Color.green);g.drawString("i am 3&qu

17、ot;,5,10); break;default:g.drawString(" 没有般配的 ",5,10);/*<APPLET CODE="Example2_10.class" WIDTH="200" HEIGHT="300"> </APPLET>*/【2_11】/* for 循环 */import javax.swing.JOptionPane;public class Example2_11public static void main(String args) int sum=0;fo

18、r(int i=1;i<=100;i+)sum=sum+i;JOptionPane.showMessageDialog(null,"1+2+3+.+100= "+sum); System.exit(0); / 退出程序【2_12】/* while 循环 */import javax.swing.JOptionPane;public class Example2_12public static void main(String args)int s=1, i=1;while(i<=10)s=s*i;i+;JOptionPane.showMessageDialog(

19、null,"1*2*3*.*10= "+s); System.exit(0); / 退出程序【2_13】/* do-while 循环 */import java.applet.*;import java.awt.*;public class Example2_13 extends Appletpublic void paint(Graphics g)int i=1;dog.drawOval(110-i*10,110-i*10,i*20,i*20); i+; while(i<=10);/*<APPLET CODE="Example2_13.class&q

20、uot; WIDTH="300" HEIGHT="300"> </APPLET>*/【2_14】/* 使用 break 语句跳出循环 */import javax.swing.JOptionPane;class Example2_14public static void main(String args)for(int i=0; i<100; i+)if(i = 10) break; / i=10 时跳出循环 JOptionPane.showMessageDialog(null,"i="+i);JOptionP

21、ane.showMessageDialog(null," 循环已经结束！ "); System.exit(0); / 退出程序2_15】/* 使用 break 语句跳出内循环 */class Example2_15public static void main(String args) for(int i=1; i<6; i+)for(int j=1;j<3; j+)if(i = 3) break; / i=5 时跳出循环 int sum=i+j;System.out.println(i+"+"+j+"="+sum); S

22、ystem.out.println(" 循环已经结束！ ");2_16】/* 使用"标签化中断 "的 break 语句跳出循环 */class Example2_16public static void main(String args)out: for(int i=1; i<6; i+) / 设置标号for(int j=1;j<3; j+)if(i = 3) break out; / i=3 时跳出循环 int sum=i+j;System.out.println(i+"+"+j+"="+sum);

23、System.out.println(" 循环已经结束！ ");2_17】/*continue 语句打印三角形 */ import javax.swing.JOptionPane; class Example2_17 public static void main(String args) String output=""for(int i=0; i<5; i+) for(int j=0; j<5; j+) if(j > i) continue ;output= output +" "+""out

24、put=output+"n"JOptionPane.showMessageDialog(null,output); System.exit(0);【2_18】/* 求一组数字的平均值 */ import javax.swing.JOptionPane;class Example2_18 public static void main(String args) double nums = 10.1, 11.2, 12.3, 13.4, 14.5; double result = 0;for(int i=0; i<5; i+) result = result + numsi; JOptionPane.showMessageDialog(null," 平均值为： " + result / 5); System.exit(0); 【2_19】/ 二维数组赋值class Example2_19public static void main(String args) int twoD= new int45;int i, j, k