习题解答
第一章 作业题
1. . public class Hello{ public static void main (String args[ ]){ System.out.pintln("早上好,good Morning"); } } 2. . import java.applet.*; import java.awt.*; public class Boy extends Applet { public void paint(Graphics g) { g.setColor(Color.blue); g.drawString("你好,hello",12,30); } }
第二章 作业题
1. .
public class erwen{ public static void main (String args[ ]){ char c='а'; System.out.println("字母"+c+"在 unicode 表中的顺序位置:"+(int)c); System.out.println("字母表:"); while(c<='я'){ System.out.print(" "+c); c=(char)(c+1); }
}
}
2. . import java.util.*; public class Zhengshu{ public static void main (String args[ ]){ Scanner reader=new Scanner(System.in); long chengji=1; int m=0; while(reader.hasNextInt()){ int x=reader.nextInt(); m=m+1; chengji=chengji*x; } System.out.println(m+"个数的乘积为"+chengji); } }
第三章
作业题
1. . import java.util.*; public class ZuoYe3_1{ public static void main (String args[ ]){ Scanner reader=new Scanner(System.in); double y=0,x=0; x=reader.nextDouble(); if(x<0) y=-1+2*x; else if(x==0) y=-1; else if(x>0) y=-1+3*x; System.out.println(y); } } 2. public class ZuoYe3_2{ public static void main(String args[]){
int sum=0,m=3,n=7,a=1; while(a<=1000){ if(a%m==0&;&;a%n==0) sum=sum+a; a++; } System.out.println("sum="+sum); } } 3. public class ZuoYe3_3 { public static void main(String args[]) { long sum=0,a=8,item=a,n=10,i=1; for(i=1;i<=n;i++) { sum=sum+item; item=item*10+a; } System.out.println(sum); } } 4. . public class ZuoYe3_4 { public static void main(String args[]) { double sum=0,a=1,b=1,fuhao=1,item=a/b; int i=1; while(i<=1000) { sum=sum+fuhao*item; i++; fuhao=fuhao*(-1); b=b+2; item=a/b; } System.out.println("sum="+sum); } }
5. . public class sum1 { public static void main(String args[]) { double sum=0,a=1; int i=1; while(i<=20) { if(i>=10) sum=sum+a; i++; a=a*i; } System.out.println("sum="+sum); } } 8. .
第四章 作业题
1. . class DengCha{ int start,d; DengCha(){ } DengCha(int start,int d){ this.start=start; this.d=d; } void setStart(int s){ start=s; } void setD(int d){ this.d=d; } int getSum(int n){
int sum=0,i=1; while(i<=n){ sum=sum+start; start=start+d; i++; } return sum; } } public class ZuoYe4_1 { public static void main (String args[ ]) { DengCha shulie=new DengCha(2,3); System.out.println(shulie.getSum(100)); shulie.setStart(10); shulie.setD(5); System.out.println(shulie.getSum(9)); } } 2. . class Letter{ public void printLetter(){ for(char c='a';c<='z';c++) System.out.print(" "+c); } } public class zimubiao { public static void main (String args[ ]) { Letter p=new Letter(); p.printLetter(); } } 3. . class SquareEquation{ double a,b;
static double c; double root1,root2; boolean boo; public SquareEquation(double a,double b,double c){ this.a=a; this.b=b; SquareEquation.c=c; if(a!=0){ boo=true; } else{ boo=false; } } public void getRoots(){ if(boo){ System.out.println("是一元 2 次方程"); double disk=b*b-4*a*c; if(di
sk>=0){ root1=(-b+Math.sqrt(disk))/(2*a); root2=(-b-Math.sqrt(disk))/(2*a); System.out.printf("方程的根:%f,%f\n",root1,root2); } else{ System.out.printf("方程没有实根\n"); } } else{ System.out.println("不是一元 2 次方程"); } } public void setCoefficient(double a,double b,double c){ this.a=a; this.b=b; SquareEquation.c=c; if(a!=0){ boo