Java语言程序设计 练习题
课本的**题目
第三章
3.4 随机月份
注意：（使用数组的时候要注意有无越界）
public class Exercise03_04 {
public static void main(String[] args) {
// TODO Auto-generated method stub
java.util.Scanner input = new java.util.Scanner(System.in);
String[] months = {
"January","February","March","April","May","June","July","August","September","October","November","December"};
System.out.println("Enter a month number(1 to 12):");
int monthNumber = input.nextInt();
System.out.println("The month is "+months[monthNumber-1]);
}
}
运行效果：（eclipse）
3.9 商业：检查ISBN-10
以下是运行示例：
Enter the first 9 digits of an ISBN as integer： 013601267
The ISBN-10 number is 013012671
Enter the first 9 digits of an ISBN as integer:013031997 The ISBN-10
number is 013031997X
public class Exercise03_09 {
public static void main(String[] args) {
// TODO Auto-generated method stub
java.util.Scanner input = new java.util.Scanner(System.in);
System.out.println("Enter the first 9 digits of an ISBN as integer：");
int number = input.nextInt();;
int total = 0;
int a = 0;
int b = number;
for(int i=9;i>0;i--) {
a = b % 10;
total += a * i;
b = b/10;
}
if((total%11)!=10) {
System.out.print("The ISBN-10 number is " + number + total%11);}
if((total%11)==10) {
System.out.print("The ISBN-10 number is " + number + "X");}
}
}
3.15 游戏：彩票
补充：
import java.util.*;
public class Exercise03_15 {
public static void main(String[] args) {
// TODO Auto-generated method stub
int lottery = (int)(Math.random()*1000);
Scanner input = new Scanner(System.in);
System.out.print("Enter your lottery pick(three digits): ");
int guess = input.nextInt();
int[] a = new int[3];
int[] b = new int[3];
int s = guess;
int t = lottery;
int win = 0;//中奖数
for(int i=0;i<3;i++) {
a[i] = s % 10;
s /=10;
}
for(int i=0;i<3;i++) {
b[i] = t % 10;
t /=10;
}
for(int i=0;i<3;i++) {
for(int j =0;j<3;j++) {
if(a[i]==b[j]) {
win++;
}}
}
if(win==1) {
System.out.println("Bouns is 1 000 dollars");
}
else if(win==3 && a[0]==b[0] && a[1]==b[1] && a[2]==b[2]) {
System.out.println("Bouns is 10 000 dollars");
}
else if(win ==3 &&(a[0]!=b[0] || a[1]!=b[1] || a[2]!=b[2])) {
System.out.println("Bouns is 3 000 dollars");
}
else {
System.out.println("No bouns!");}
System.out.print("The lottery is "+lottery);
input.close();
}
}
3.19(计算三角形的周长)
import java.util.*;
public class Exercise03_19 {
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner input = new Scanner(System.in);
System.out.print("Enter three numbers: ");
int a = input.nextInt();
int b = input.nextInt();
int c = input.nextInt();
int cir = 0;
if(a+b>c && a+c>b && b+c>a) {
cir = a+b+c;
System.out.print("circumference is "+cir);
}
else {
System.out.print("Can't form a triangle");}
input.close();
}
}
3.21（科学：某天是星期几）
public class Exercise03_21 {
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner input = new Scanner(System.in);
System.out.print("Enter year: (e.g.,2012): ");
int year = input.nextInt();
System.out.print("Enter month: 1-12: ");
int month = input.nextInt();
if(month ==1) {
month=13; year=year-1;}
if(month ==2) {
month=14; year=year-1;}
System.out.print("Enter the day of the month: ");
int day = input.nextInt();
int century = year / 100;
int yearOfCentury = year % 100;
int h = (day + 26 * (month + 1) / 10 + yearOfCentury + yearOfCentury / 4 + century / 4 + 5 * century) % 7;;
System.out.print("Day of the week is ");
if(h==0) {
System.out.print("Saturday");}
else if(h==1) {
System.out.print("Sunday");}
else if(h==2) {
System.out.print("Monday");}
else if(h==3) {
System.out.print("Tuesday");}
else if(h==4) {
System.out.print("Wednesday ");}
else if(h==5) {
System.out.print("Thursday");}
else if(h==6) {
System.out.print("Friday");}
input.close();
}
}
3.22（几何：点是否在圆内？）
package firstprogram;
import java.util.*;
public class Exercise03_22 {
public static void main(String[] args) {
System.out.print("Enter a point with two coordinates: ");
Scanner in = new Scanner(System.in);
float x= in.nextInt();
float y= in.nextInt();
double d= Math.sqrt(x*x+y*y);
if(d<=10) {
System.out.print("Point ("+x+", "+y+" ) is in the circle");
}
else {
System.out.print("Point ("+x+", "+y+" ) is not in the circle");
}
in.close();
}}
3.23 点是否在矩形内？
public class Exercise03_23 {
public static void main(String[] args) {
System.out.print("Enter a point with two coordinates: ");
Scanner in = new Scanner(System.in);
float x= in.nextInt();
float y= in.nextInt();
if(x<5&& x>(-5) && y<2.5 && y>(-2.5)) {
System.out.print("Point ("+x+", "+y+" ) is in the rectangle");
}
else {
System.out.print("Point ("+x+", "+y+" ) is not in the rectangle");
}
in.close();
}}
3.24游戏：挑一张牌
public class Exercise03_24 {
public static void main(String[] args) {
System.out.print("Enter a number: ");
Scanner in = new Scanner(System.in);
int x= in.nextInt();
in.close();
int d=x/13;
int s=x%13;
String[] suits= {
"Clubs","Diamonds","Hearts","Spades"};
String[] ranks= {
"Ace","2","3","4","5","6","7","8","9","10","Jack","Queen","King"};
System.out.print("The card you picked is "+ranks[s]+" of "+suits[d-1]);
}}
3.28几何：两个矩形
public class Exercise03_28 {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
System.out.print("Enter rl's center x-, y-coordinates, width , and height: ");
double x1= in.nextDouble();
double y1= in.nextDouble();
double w1= in.nextDouble();
double h1= in.nextDouble();
System.out.print("Enter r2's center x-, y-coordinates, width , and height: ");
double x2= in.nextDouble();
double y2= in.nextDouble();
double w2= in.nextDouble();
double h2= in.nextDouble();
in.close();
if(x2-w2/2>=x1-w1/2 && x2+w2/2<=x1+w1/2 && y2-h2/2>=y1-h1/2 && y2+h2/2<=y1+h1/2) {
System.out.print("r2 is inside rl");
}
else if(x2-w2/2<x1-w1/2 || x2+w2/2>x1+w1/2 || y2-h2/2<y1-h1/2 || y2+h2/2>y1+h1/2) {
System.out.print("r2 does not overlap rl");
}
else {
System.out.print("r2 overlaps rl");
}
}}
3.29 几何：两个圆
public class Exercise03_29 {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
System.out.print("Enter circlel's center x-, y-coordi nates, and radius: ");
double x1= in.nextDouble();
double y1= in.nextDouble();
double r1= in.nextDouble();
System.out.print("Enter circle2 's center x-, y-coordinates, and radius: ");
double x2= in.nextDouble();
double y2= in.nextDouble();
double r2= in.nextDouble();
in.close();
double d=Math.sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
double d2=Math.abs(r1-r2);
if(d<=d2) {
System.out.print("circle2 is inside circlel");
}
else if(d<=r1+r2) {
System.out.print("circle2 overlaps circlel");
}
else {
System.out.print("circle2 does not overlap circlel");
}
}}
补充1.出现’input’ is never closed的警告
可以在代码最后加一句：
input.close();