目录
Java练习第二章
7-21 统计符合条件元素的个数
7-210 sdut-array2-1-矩阵转置（I）
7-211 JAVA-输入输出入门
7-212 sdut-入门-三个整数和、积与平均值
7-213 jmu-java-m01-System.out.printf入门
7-214 jmu-java-m02-循环求和
7-215 编程题：统计符合条件元素的个数
7-216 jmu-java-m02-数组基本操作
7-22 整数数组比较-Java
7-23 求n以内所有能被3和5整除的正整数
7-24 输出所有的水仙花数
7-25 编写一个程序解决爱因斯坦台阶问题
7-26 判断一个数是否为回文数
7-27 编写程序求1000之内的所有完全数。
7-28 编写Java程序，求13-23+33-43+…+973-983+993-1003的值。
7-29 用foreach求数组之和
Java练习第三章
6-31 定义复数类Complex
6-32 比较两个对象是否相等
6-33 利用静态变量实现自动编号
6-34 编写一个单例类
6-35 定义派生类Rectangle
6-36 编写雇员工资支付程序。
6-37 图书和音像租赁
6-38 定义商品类
6-39 实现部门介绍功能需求说明（继承）
6-310 高速公路车辆收费系统（继承）
6-311 模拟控制动物叫的功能（多态）
6-312 使用多态实现图书馆计算罚金功能
7-31 设计一个People类
7-32 定义商品类，封装成员变量，输出对象
7-33 单例类练习
Java练习第二章
7-21 统计符合条件元素的个数
import java.util.Scanner;public class Main {public static void main(String[] args) {Scanner scan = new Scanner(System.in);int n = scan.nextInt();//计算能被3整除的奇数和偶数int s = 0;int d = 0;for (int i = 1; i <= n; i++) {if(i % 3 == 0) {if(i % 2 == 0) {d++;}elses++;}}System.out.println(s + "," + d);}
}7-210 sdut-array2-1-矩阵转置（I）
import java.util.Scanner;public class Main{public static void main(String[] args) {Scanner scanner = new Scanner(System.in);int N = scanner.nextInt();int[][] arr = new int[N][N];for (int i = 0; i < N; i++) {for (int j = 0; j < N; j++) {arr[i][j] = scanner.nextInt();}}for (int i = 0; i < N; i++) {for (int j = 0; j < N; j++) {System.out.print(arr[j][i]);if(j < N -1)System.out.print(" ");}System.out.println();}}
}7-211 JAVA-输入输出入门
import java.io.*;
import java.util.Scanner;
class Main{public static void main(String[] args) {Scanner scan = new Scanner(System.in);int x = scan.nextInt();double y = scan.nextDouble();System.out.println(x + y);System.out.println(Math.sqrt(x + y));System.out.print(String.format("%.6f",Math.sqrt(x+y)));}
}7-212 sdut-入门-三个整数和、积与平均值
import java.io.*;
import java.util.Scanner;class Main {public static void main(String[] args)throws IOException {Scanner scan = new Scanner(System.in);int a = scan.nextInt();int b = scan.nextInt();int c = scan.nextInt();System.out.print((a + b + c)+" ");System.out.print((a * b * c) + " ");System.out.print(String.format("%.2f",((a+b+c)/3.0)));}
}
7-213 jmu-java-m01-System.out.printf入门
import java.util.Scanner;public class Main {public static void main(String[] args) {Scanner s = new Scanner(System.in);int a = s.nextInt();double b = s.nextDouble();int x1 = s.nextInt();int x2 = s.nextInt();int x3 = s.nextInt();System.out.println(a+" "+Integer.toOctalString(a)+" "+Integer.toHexString(a));System.out.println(String.format("%6.2f", b));System.out.println(String.format("%5d",x1)+" "+String.format("%5d",x2)+" "+String.format("%5d",x3));System.out.println(String.format("%5d",x2)+" "+String.format("%5d",x3)+" "+String.format("%5d",x1));System.out.println(String.format("%5d",x3)+" "+String.format("%5d",x1)+" "+String.format("%5d",x2));}
}7-214 jmu-java-m02-循环求和
import java.io.*;
import java.util.Scanner;class Main{public static void main(String[]args){Scanner s = new Scanner(System.in);int n = s.nextInt();int[] arr = new int[n];int sum1 = 0;int sum2 = 0;for (int i = 0; i < n; i++) {arr[i] = s.nextInt();if(arr[i] % 2 == 0) {sum2+=arr[i];}elsesum1+=arr[i];}System.out.println("奇数和="+sum1+", 偶数和="+sum2);}
}7-215 编程题：统计符合条件元素的个数
import java.io.*;
import java.util.Scanner;
class Main{public static void main(String[] args) {Scanner scan = new Scanner(System.in);int n = scan.nextInt();int s = 0;int d = 0;for (int i = 1; i <= n; i++) {if(i % 3 == 0) {if(i % 2 ==0)d++;elses++;}}System.out.println(s + "," + d);}
}
7-216 jmu-java-m02-数组基本操作
import java.util.Scanner;
import java.util.Arrays;
public class Main{public static void main(String[] args) {Scanner scan = new Scanner(System.in);int n = scan.nextInt();int[] R = new int[n];for (int i = 0; i < n; i++) {R[i] = scan.nextInt();}//排序Arrays.sort(R);System.out.println(Arrays.toString(R));//逆序for (int i = R.length-1; i >= 0 ; i--) {System.out.print(R[i]+" ");}System.out.println();//平均半径double mid= Arrays.stream(R).sum()/(double)n;System.out.println("平均半径="+mid);//总面积double area = 0;for (int x:R) {area+=x*x*Math.PI;}System.out.println("总面积="+String.format("%.6f",area));}
}7-22 整数数组比较-Java
import java.util.Arrays;
import java.util.Scanner;public class Main {public static void main(String[] args) {Scanner scan = new Scanner(System.in);int n = scan.nextInt();int[] A = new int[n];for (int i = 0; i < n; i++) {A[i] = scan.nextInt();}int[] B = A.clone();Arrays.sort(B);int ab = 0;int ba = 0;int d = 0;for (int i = 0; i < n; i++) {if(A[i] > B[i]) {ab++;}else if(A[i] < B[i]) {ba++;}elsed++;}System.out.println(ab);System.out.println(d);System.out.println(ba);}
}
7-23 求n以内所有能被3和5整除的正整数
import java.io.*;
import java.util.Scanner;class Main{public static void main(String[]args){Scanner scan = new Scanner(System.in);int n = scan.nextInt();int key = 0;for (int i = 1; i <= n; i++) {if(i % 3 == 0 && i % 5 == 0) {System.out.print(i+" ");key++;}if(key == 10) {System.out.println();key -= 10;}}}
}7-24 输出所有的水仙花数
import java.io.*;class Main{public static void main(String[]args){for (int i = 100; i < 1000; i++) {int a = i % 10;int b = i / 10 % 10;int c = i / 100;if(a*a*a + b*b*b + c*c*c == i) {System.out.println(i);}}}
}7-25 编写一个程序解决爱因斯坦台阶问题
public class Main{public static void main(String[]args){int x = 1;while(true) {if(x % 2 == 1 && x % 3 == 2 && x % 4 ==3&&x % 5 == 4 && x % 6 ==5 && x% 7 == 0) {System.out.println(x);break;}x++;}}
}7-26 判断一个数是否为回文数
import java.util.Scanner;
public class Main {public static void main(String[] args) {Scanner scan = new Scanner(System.in);int n = scan.nextInt(); //n是要判断的数int num = 1; //num有几位数int key = 1; //key用于计算int tmp = n;while(tmp > 10) {tmp /= 10;num++;key *= 10;}tmp = n;while(tmp > 10) {int a = tmp / key;int b = tmp % 10;if(a != b) {System.out.println(n + " 不是回文数");return;}tmp%=key;tmp/=10;key/=100;}System.out.println(n + " 是回文数");}
}7-27 编写程序求1000之内的所有完全数。
class Main{public static void main(String[] args) {for (int i = 1; i < 1000; i++) {int sum = 0;for (int j = 1; j < i; j++) {if(i % j == 0) {sum += j;}}if(sum == i) {System.out.print(i+" ");}}}
}7-28 编写Java程序，求13-23+33-43+…+973-983+993-1003的值。
class Main {public static void main(String[] args) {int sum = 0;int k = 1;for (int i = 13; i <= 1003; i+=10) {sum += i * k;k *= -1;}System.out.println(sum);}
}7-29 用foreach求数组之和
import java.util.Scanner;
public class Main{public static void main(String[] args) {Scanner scan = new Scanner(System.in);int n = scan.nextInt();int[] arr = new int[n];for (int i = 0; i < n; i++) {arr[i] = scan.nextInt();}int sum = 0;for(int x:arr) {sum+=x;}System.out.println(sum);}
}
Java练习第三章
6-31 定义复数类Complex
class Complex {double a;double b;public Complex(double a,double b) {this.a = a;this.b = b;}public Complex add(Complex c) {Complex tmp = new Complex(this.a,this.b);tmp.a+=c.a;tmp.b+=c.b;return tmp;}public Complex sub(Complex c) {Complex tmp = new Complex(this.a,this.b);tmp.a-=c.a;tmp.b-=c.b;return tmp;}public String getString() {return "("+a+","+b+"i)";}
}6-32 比较两个对象是否相等
class Bird {String color;int size;public Bird(String color, int size) {this.color = color;this.size = size;}public String equals(Bird b) {if(this.color == b.color && this.size == this.size)return "同一只鸟";return "不同一只鸟";}
}6-33 利用静态变量实现自动编号
class Book {String name;double price;int id;public static int num = 0;public Book() {num++;id=num;}public Book(String name, double price) {this();this.name = name;this.price = price;}public String toString() {return "编号：" +id+"，书名：" + name +"，价格：" + price;}
}6-34 编写一个单例类
class SingleTest {private static int bucket = 100;private static SingleTest test = new SingleTest();public static SingleTest getInstance() {return test;}public void addobj() {System.out.println("当前的储量是"+(++bucket));}public void delOjb() {System.out.println("当前的储量是"+(--bucket));}
}6-35 定义派生类Rectangle
class Rectangle extends Shape {protected double width;protected double height;public Rectangle(double width, double height) {this.width = width;this.height = height;}public Rectangle(int id, String color, double width, double height) {super(id, color);this.width = width;this.height = height;}@Overridepublic void area() {System.out.println(width * height);}
}6-36 编写雇员工资支付程序。
class Manager extends Employee{private int salary;public Manager(String name, String type, int salary) {super(name, type);this.salary = salary;}@Overridepublic int getSalary() {return salary;}
}class Salesman extends Employee {private int salary;private int salaryRaise;public Salesman(String name, String type, int salary, int salaryRaise) {super(name, type);this.salary = salary;this.salaryRaise = salaryRaise;}@Overridepublic int getSalary() {return salary+salaryRaise;}
}
class Worker extends Employee {private int salary;private int days;public Worker(String name, String type, int salary, int days) {super(name, type);this.salary = salary;this.days = days;}public int getSalary() {return salary*days;}
}6-37 图书和音像租赁
class Media {double getDailyRent() {return 0;}
}
class Book extends Media {String name;double price;public Book(String name, double price) {this.name = name;this.price = price;}double getDailyRent() {return price*0.01;}
}
class DVD extends Media {String name;public DVD(String name) {this.name = name;}double getDailyRent() {return 1.0;}
}
class MediaShop extends Media {static double calculateRent(Media[] medias, int days) {double sum = 0;for (int i = 0; i < medias.length; i++) {sum+=medias[i].getDailyRent()*days;}return sum;}
}6-38 定义商品类
class Goods {private String id;private String name;private double price;public Goods(String id, String name, double price) {this.id = id;this.name = name;this.price = price;}@Overridepublic String toString() {return id + "," + name + "," + price ;}public String getId() {return id;}public void setId(String id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public double getPrice() {return price;}public void setPrice(double price) {this.price = price;}
}6-39 实现部门介绍功能需求说明（继承）
class Department {private String sector;private String name;private int num;private String work;public Department(String sector, String name, int num, String work) {this.sector = sector;this.name = name;this.num = num;this.work = work;}public String printIntro() {return "部门名称："+sector+"\n"+"经理："+name+"\n"+"员工人数："+num+"\n"+"部门职责："+work+"\n";}
}class HR extends Department {private int plan;public HR(String sector, String name, int num, String work, int plan) {super(sector, name, num, work);this.plan = plan;}@Overridepublic String printIntro() {return super.printIntro()+"招聘目标："+plan+"人";}
}
class RD extends Department {private int number;public RD(String sector, String name, int num, String work, int number) {super(sector, name, num, work);this.number = number;}@Overridepublic String printIntro() {return super.printIntro()+"研发项目数:"+number+"人";}
}6-310 高速公路车辆收费系统（继承）
class Vehicle {int length;String plateNo;public Vehicle(int length, String plateNo) {this.length = length;this.plateNo = plateNo;}public Vehicle(int length) {this.length = length;}public String getString() {return "车牌号："+plateNo+"\n"+"车长："+length+"\n";}public double getRate() {return 0;}
}
class Bus extends Vehicle{int passengers;public Bus(int length, String plateNo, int passengers) {super(length, plateNo);this.passengers = passengers;}@Overridepublic String getString() {return super.getString()+"核定载人数："+passengers;}@Overridepublic double getRate() {if(length < 6000) {return 0.6;}else {return 0.9;}}
}
class Truck extends Vehicle {double weight;int numbersOfAxles;public Truck(int length, String plateNo, double weight, int numbersOfAxles) {super(length, plateNo);this.weight = weight;this.numbersOfAxles = numbersOfAxles;}@Overridepublic String getString() {return super.getString()+"最大允许总重量："+weight+"\n"+"车轴数:"+numbersOfAxles;}@Overridepublic double getRate() {if(numbersOfAxles == 2) {if(length < 6000 && weight < 4500)return 0.6;elsereturn 0.9;}if (numbersOfAxles == 3)return 1.02;if(numbersOfAxles == 4)return 1.315;if(numbersOfAxles == 5 || numbersOfAxles == 6)return 1.428;elsereturn -1;}
}6-311 模拟控制动物叫的功能（多态）
class Animal {public void cry() {System.out.println("动物叫......");}
}
class Dog extends Animal {@Overridepublic void cry() {System.out.println("汪汪汪......");}
}
class Cat extends Animal {@Overridepublic void cry() {System.out.println("喵喵喵......");}
}
class Duck extends Animal {@Overridepublic void cry() {System.out.println("嘎嘎嘎......");}
}
class Host {public void letCry(Animal animal) {animal.cry();}
}6-312 使用多态实现图书馆计算罚金功能
class Book {String name;int borrowDays;public Book(String name) {this.name = name;}public int calFines(int borrowDays) {return 0;}public String getName() {return name;}
}
class AdultBook extends Book {public AdultBook(String name) {super(name);}@Overridepublic int calFines(int borrowDays) {int num = borrowDays - 21;if(num <= 0)return 0;if(num <= 3)return num * 2;elsereturn (num - 3) * 5 + 3 * 2;}
}
class KidBook extends Book {public KidBook(String name) {super(name);}public int calFines(int borrowDays) {int num = borrowDays - 21;if(num <= 0)return 0;elsereturn num;}
}
class Disc extends Book {public Disc(String name) {super(name);}public int calFines(int borrowDays) {int num = borrowDays - 14;if(num <= 0)return 0;if(num <= 3)return num * 5;elsereturn (num - 3) * 10 + 3 * 5;}
}
class Customer {public double calTotalFines(Book books[], int borrowDays) {int sum = 0;for (int i = 0; i < books.length; i++) {sum += books[i].calFines(borrowDays);}return sum;}
}7-31 设计一个People类
public class Main {public static void main(String[] args) {/********* begin *********/// 声明并实例化一Person对象pPerson p = new Person();// 给p中的属性赋值p.setName("张三");p.setAge(18);// 调用Person类中的talk()方法p.talk();/********* end *********/}
}// 在这里定义Person类
class Person {private String name;private int age;public void talk() {System.out.println("我是："+name+"，今年："+age+"岁");}public String getName() {return name;}public int getAge() {return age;}public void setName(String name) {this.name = name;}public void setAge(int age) {this.age = age;}
}7-32 定义商品类，封装成员变量，输出对象
class Shop {private String id;private String name;private double price;public Shop(String id ,String name,double price) {this.id=id;this.name=name;this.price=price;}public String toString() {return id+","+name+","+price;}public String getId() {return id;}public String getName() {return name;}public double getPrice() {return price;}public void setId(String id) {this.id = id;}public void setName(String name) {this.name = name;}public void setPrice(double price) {this.price = price;}
}public class Main {public static void main(String[] args) {Shop s = new Shop("WJ002","记事本",5.5);System.out.println(s.toString());}
}7-33 单例类练习
class Printer {String number;double price;private static Printer P = new Printer("惠普",3400);private Printer(String number,double price) {this.price=price;this.number=number;}public static Printer getPrinter() {return P;}public String toString() {return "型号为："+number+",价格为："+price;}
}
public class Main {public static void main(String[] args) {Printer P = Printer.getPrinter();System.out.println(P.toString());}
}
