Java 书后程序题答案(清华大学出版社)

Java 书后程序题

第二章

3 （1）

class wanquanshu{

public static void main(String[] args) {

int num = 2;

int sum = 0;

//找出因数

while(num<=1000){

sum=0;

for(int i =1;i

if(num%i==0)

sum+=i;

}

if(num==sum)

System.out.print(num+" ");

num++;

}

}

}

（2）class shuixian{

public static void main(String[] args) {

for(int i=100;i<=999;i++) {

int geWei,shiWei,baiWei;

baiWei=i/100;

shiWei=(i-baiWei*100)/10;

geWei=i-baiWei*100-shiWei*10;

if (i==geWei*geWei*geWei+shiWei*shiWei*shiWei+baiWei*baiWei*baiWei) System.out.println(i);}}

}

（3）class xing{

public static void main(String args[]){

for (int x=1;x<7;x++){

for (int z=1;z<7-x;z++)

System.out.print(" ");

for (int y=1;y<=x;y++)

System.out.print("* ");

System.out.println();

}

}}

3 （2）

class P87_3_2{

public static void main(String args[]){

int [] jifen={15,28,10,26,13,45,67,60};

int min=100,t=0;

for (int i=0;i

{ if (jifen[i]

{min=jifen[i];

t=i; }}

System.out.println("积分最少"+jifen[t]+"所在位置是"+t+1);

}}

（3）

import java.util.*;

class P87_3_3{

public static void main(String args[]){

Scanner input=new Scanner(System.in);

String s=input.next();

int t=s.length();

String xing=s.substring(0,1);

String ming=s.substring(1,t);

System.out.println("姓"+xing+"名"+ming);

}}

第四章

3（1）public class ExPoint1{

public static void main(String args[])

{Point p1=new Point(3,3);

p1.move(3,3);

p1.printxy();}}

class Point

{float x;

float y;

Point (float a,float b){x=a;y=b;}

Point(){this(0,0);}

void move(int a,int b ){x=x+a;y=y+b;}

float getx(){return x;}

float gety(){return y;}

void printxy(){System.out.println("当前点的坐标值分别为"+x+" "+y);} }

abstract class tuxing{

abstract double f();

abstract double area();}

class san extends tuxing{

float a,b,c;

san(float a,float b,float c){this.a=a;this.b=b;this.c=c;}

double area(){

double t,l;

l=(a+b+c)/2;

t=Math.sqrt(l*(l-a)*(l-b)*(l-c));

return t;}

double f(){return a+b+c;}

public static void main(String args[]){

san s1=new san(3.0f,4.0f,5.0f);

System.out.println("周长为"+s1.f()+"面积为"+s1.area());}}

（3）class Data{

int year;

int month;

int day;

Data(int x,int y,int z)

{year=x;month=y;day=z;}}

class bank{

String 账号;

String 姓名;

String 身份证号;

float 余额;

Data 开户时间;

bank(String a,String b,String c,float d,Data e)

{this.账号=a;姓名=b; 身份证号=c; 余额=d; 开户时间=e;}

void 取款(float t){ 余额=余额-t;}

void 存款(float t ){ 余额=余额+t;}

void 查询明细(){System.out.println("姓名"+姓名+"的身份证号是"+身份证号+"卡内余额是"+余额);}

public static void main(String args[]){

bank b1=new bank("1401","张三","2250582827171",1000.00f,new Data(2014,3,2));

b1.查询明细();

b1.取款(200f);

b1.查询明细();

b1.存款(500f);

b1.查询明细();

}}

2 （1）interface Area{

float pai=3.14f;

float area();}

class Ellipse implements Area{

float a,b;

Ellipse(float t1,float t2){a=t1;b=t2;}

public float area(){return pai*a*b;}

void printarea(){System.out.println("此椭圆的面积为"+area());}} class testarea{

public static void main(String args[]){

Ellipse E1=new Ellipse(2.0f,3.0f);

E1.printarea();}}

（2）interface PCI{

void know();

boolean powerOnOff(boolean b);}

class SoundCard{

boolean power;

String sMaker="";

SoundCard(String a,boolean t){sMaker=a;power=t;}

void know(){System.out.println("系统已兼容");}

boolean powerOnOff(boolean b){

this.power=b;

System.out.println(sMaker+"设备状态："+(this.power?"开":"关")); return this.power;}

void setpower(boolean t){power=!power;}

boolean getpower(){return power;}}

class NetworkCard{

boolean power;

String sMaker="";

NetworkCard(String a,boolean t){sMaker=a;power=t;}

void know(){System.out.println("系统已兼容");}

boolean powerOnOff(boolean b){

this.power=b;

System.out.println(sMaker+"设备状态："+(this.power?"开":"关")); return this.power;}

void setpower(boolean t){power=!power;}

boolean getpower(){return power;}}

class TestPCI{

public static void main(String args[]){

SoundCard s=new SoundCard("联想",false);

NetworkCard n=new NetworkCard("Dell",true);

s.know();

s.setpower(true);

System.out.println("当前设备的状态是"+s.getpower());

s.powerOnOff(false);

n.know();

n.setpower(false);

System.out.println("当前设备的状态是"+s.getpower());

n.powerOnOff(true);}}

第六章

3 （1）class ExceptionTest1{

public static void main(String args[]){

int a=5,b=0,c;

try{

c=a/b;}

catch(ArithmeticException e){

System.out.println("除数为零，不能计算");

}finally{

System.out.println("请重新调整程序中的数据");}}}

（2）

class ExceptionTest2{

public static void main(String args[]){

int a[]={1,2,3};

try{

a[5]=4;}

catch(ArithmeticException e){

System.out.println("除数为零，不能计算");}

catch(ArrayIndexOutOfBoundsException r) {

System.out.println("下标越界");}

catch(Exception e){

System.out.println("程序出错，请修改程序");}

finally{

System.out.println("请重新调整程序中的数据");}}}

第七章

3（1）//此程序是作业第3（1）题的第1问，根目录时将path的路径改为c:\\ import java.io.*;

public class TestFileDirectory1{

public static void main(String[] args) {

String[] list;

File path = new File("E:\\jdk\\bin");

File path1=path.getParentFile();

if (args.length > 0)

list = path1.list(new MyFilter(args[0]));

else

list = path1.list();

for (int i = 0; i < list.length; i++) {

System.out.println(list[i]);

}

System.out.println("总共有" + list.length + "文件或文件夹。");

}

}

class MyFilter implements FilenameFilter {

String pattern;

MyFilter(String pattern) {

this.pattern = pattern;

}

public boolean accept(File dir, String name) {

return (name.indexOf(pattern) >= 0);

}

//此程序是作业第3（1）题的第2问

import java.io.*;

import java.util.Scanner;

public class TestFileDirectory2{

public static void main(String[] args) {

String[] list;

Scanner sc=new Scanner(System.in);

File path = new File("E:\\jdk\bin");

File path1=path.getParentFile();

String t;

t=sc.next();

list = path1.list(new MyFilter(t));

for (int i = 0; i < list.length; i++) {

System.out.println(list[i]);

}

System.out.println("总共有" + list.length + "文件或文件夹。");

}

}

class MyFilter implements FilenameFilter {

String pattern;

MyFilter(String pattern) {

this.pattern = pattern;

}

public boolean accept(File dir, String name) {

return (name.indexOf(pattern) >= 0);

}

}

（2）

import java.io.*;

class ExampleData{

public static void main(String args[]) throws IOException {String file="data.dat";

FileOutputStream out=new FileOutputStream(file); DataOutputStream dataOut=new DataOutputStream(out); dataOut.writeInt(32);

dataOut.writeDouble(32.2);

dataOut.writeChar('a');

out.close();

dataOut.close();

FileInputStream in=new FileInputStream(file); DataInputStream dataIn=new DataInputStream(in);

int a=dataIn.readInt();

double b=dataIn.readDouble();

char c=dataIn.readChar();

System.out.println(a+" "+b+" "+c);

in.close();

dataIn.close();

}}