java习题

7-12 图形继承 (20 分)

import java.util.Scanner;

class Shape //定义一个无自身属性，有一个返回值为0.0的求面积方法
{

	public Shape() 
	{
       System.out.println("Constructing Shape");
	}
	public double getArea()
	{
	   return 0.0;
	}
}

class Circle extends Shape//继承自Shape
{
	public Circle() 
	{
       System.out.println("Constructing Circle");
	}
	private double radius;//新定义一个半径
	
	public void setRadius(double radius) {// 设置半径
		this.radius = radius;
	}
	
	public double getRadius() {// 获取半径
		return radius;
	}
	
	@Override
	public double getArea() {
		// TODO Auto-generated method stub
		return Math.PI*radius*radius;//重写父类的方法
	}
	
}
class Rectangle extends Shape
{
	public Rectangle() 
	{
       System.out.println("Constructing Rectangle");
	}
	private double width;
	private double length;
	public double getWidth() {
		return width;
	}

	public void setWidth(double width) {
		this.width = width;
	}

	public double getLength() {
		return length;
	}

	public void setLength(double length) {
		this.length = length;
	}

	@Override
	public double getArea() {
		// TODO Auto-generated method stub
		return width*length;
	}
	
}
class Ball extends Circle
{
	public Ball() 
	{
       System.out.println("Constructing Ball");
	}

	@Override
	public double getArea() {
		// TODO Auto-generated method stub
		return 4.0*super.getArea();//方法的重载，super关键字
	}
	public double getVolume()
	{
		double r2=getRadius();
		return 4.0/3.0*r2*r2*r2*Math.PI;
	}
	
}
class Box extends Rectangle
{
	public Box() 
	{
       System.out.println("Constructing Box");
	}
	private double height;
	public double getHeight() {
		return height;
	}
	public void setHeight(double height) {
		this.height = height;
	}
	public double getVolume()
	{
		return height*super.getArea();
	}
	@Override
	public double getArea() {
		// TODO Auto-generated method stub
		double w2=getWidth();
		double l2=getLength();
		return 2*(w2*l2+w2*height+l2*height);
	}
	
	
}
public class Main {

	public static void main(String[] args) {
		int inType;
		Scanner scanner=new Scanner(System.in);
		inType=scanner.nextInt();
		switch(inType)
		{
		case 1:
			double r=scanner.nextDouble();
			if(r<0.0) {
				System.out.println("Wrong Format");
			}
			else {
				Circle circle=new Circle();
				circle.setRadius(r);
				System.out.println(String.format("Circle's area:%.2f",circle.getArea()));
			}
			break;
		
		case 2:
			double width=scanner.nextDouble();
			double length=scanner.nextDouble();
			if(width<0.0||length<0.0) {
				System.out.println("Wrong Format");
			}
			else {
				Rectangle rectangle=new Rectangle();
				rectangle.setLength(length);
				rectangle.setWidth(width);
				System.out.println(String.format("Rectangle's area:%.2f",rectangle.getArea()));
			}
			break;
		case 3:
			double r2=scanner.nextDouble();
			if(r2<0.0) {
				System.out.println("Wrong Format");
			}
			else {
				Ball ball=new Ball();
				ball.setRadius(r2);
				System.out.println(String.format("Ball's surface area:%.2f",ball.getArea()));
				System.out.println(String.format("Ball's volume:%.2f",ball.getVolume()));
			}
			break;
		case 4:
			double width2=scanner.nextDouble();
			double length2=scanner.nextDouble();
			double height=scanner.nextDouble();
			if(width2<0.0||length2<0.0||height<0.0) {
				System.out.println("Wrong Format");
			}
			else {
				Box box=new Box();
				box.setHeight(height);
				box.setWidth(width2);
				box.setLength(length2);
				System.out.println(String.format("Box's surface area:%.2f",box.getArea()));
				System.out.println(String.format("Box's volume:%.2f",box.getVolume()));
			}
			break;
		default:
			System.out.println("Wrong Format");
		}
	}
	}

7-13 jmu-Java-03面向对象基础-04-形状-继承 (15 分)

import java.util.Scanner;
 
abstract class Shape {
	double PI = 3.14;
 
	public abstract double getPerimeter();
 
	public abstract double getArea();
}
 
class Rectangle extends Shape {
	int wide, len;
 
	Rectangle(int a, int b) {
		wide = a;
		len = b;
	}
 
	@Override
	public double getPerimeter() {
		// TODO Auto-generated method stub
		return 2 * (wide + len);
	}
 
	@Override
	public double getArea() {
		// TODO Auto-generated method stub
		return wide * len;
	}
	
	public String toString(){
		return "[width=" + wide + ", length=" + len + "]";
	}
}
 
class Circle extends Shape {
	int radius;
 
	Circle(int _radius) {
		radius = _radius;
	}
 
	@Override
	public double getPerimeter() {
		// TODO Auto-generated method stub
		return radius * 2 * PI;
	}
 
	@Override
	public double getArea() {
		// TODO Auto-generated method stub
		return radius * radius * PI;
	}
 
	public String toString(){
		return "[radius=" + radius + "]";
	}
 
}
 
public class Main {
	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		int n = in.nextInt();
		in.nextLine();
		Shape A[] = new Shape[n];
		int k = 0, j = 0;
		double sumAllArea = 0, sumAllPerimeter = 0;
		for (int i = 0; i < n; i++) {
			String S = in.next();
			if (S.equals("rect")) {
				int wide = in.nextInt(), len = in.nextInt();
				in.nextLine();
				A[i] = new Rectangle(wide, len);
			} else if (S.equals("cir")) {
				int radius = in.nextInt();
				in.nextLine();
				A[i] = new Circle(radius);
			}
			sumAllArea += A[i].getArea();
			sumAllPerimeter += A[i].getPerimeter();
		}
 
		System.out.println(sumAllPerimeter);
		System.out.println(sumAllArea);
		System.out.print("[");
		for (int i = 0; i < n; i++) {
			if(i != 0)
				System.out.print(", ");
			if (A[i] instanceof Rectangle) {
					System.out.print("Rectangle ");
				System.out.print(A[i].toString());
			}
			else {
					System.out.print("Circle ");
				System.out.print(A[i].toString());	
			}
		}
 
		System.out.println("]");
 
		for(int i = 0;i < n;i++) {
			if(A[i] instanceof Rectangle) {
				System.out.println("class Rectangle,class Shape");
			}else {
				System.out.println("class Circle,class Shape");
 
			}
		}
		in.close();
	}
}

7-15 集体评分2 (10 分)

import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
                Scanner in = new Scanner(System.in);
                int[] grade = new int[5];
                for(int i=0; i<grade.length; i++){
                      grade[i] = in.nextInt();
                 }

                RR rr = new RT(grade);
                double dd = rr.mark();
                System.out.printf("%.2f",dd);
    }
}
interface RR{
   double mark();
}
class RT implements RR{
   int[] grade;
   public double mark() {
	   double max=0;
	   double min=0x3f3f3f3f;
	   double sum=0;
	   for(int i: grade) {
		   sum+=i;
		   if(i>max)max=i;
		   if(i<min)min=i;
	   }
	   sum-=(max+min);
	   sum/=(double)(grade.length-2);
	   return sum;
   }
   public RT(int[] grade){
      this.grade = grade;
   }
}

7-16 程序改错题2 (5 分)

public class Main {
    public static void main(String[] args) {
        Dog animal = new Dog();
        animal.shout();
        animal.run();
    }
}

class Animal {
    void shout() {
        System.out.println("animal shout！");
    }
}

class Dog extends Animal {
    void shout() {
        super.shout();
        System.out.println("wangwang……");
    }

    void run() {
        System.out.println("Dog is running");
    }
}

7-17 程序填空题3 (5 分)

import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Son son = new Son();
        son.method();
    }
}

class Parent {
    Parent() {
        System.out.println("Parent's Constructor without parameter");
    }

    Parent(boolean b) {
        System.out.println("Parent's Constructor with a boolean parameter");
    }

    public void method() {
        System.out.println("Parent's method()");
    }
}

class Son extends Parent {
    //补全本类定义
	Son(){
		super(true);
		System.out.println("Son's Constructor without parameter");
	}
	public void method() {
//		super.method();
		System.out.println("Son's method()");
		super.method();
	}
}

7-18 接口–四则计算器 (10 分)

import java.util.*;

interface ICompute{
	int compute(int x,int y);
}

class Add implements ICompute{
	@Override
	public int compute(int x, int y) {
		// TODO Auto-generated method stub
		return x+y;
	}
}

class Sub implements ICompute{
	@Override
	public int compute(int x, int y) {
		// TODO Auto-generated method stub
		return x-y;
	}
}

public class Main {
    public static void main(String[] args) {
       Scanner in = new Scanner(System.in);
       int a=in.nextInt(),b=in.nextInt();
       Add x=new Add();
       Sub y=new Sub();
       System.out.println(x.compute(a,b));
       System.out.println(y.compute(a, b));
    }
}

7-19 成绩录入时的及格与不及格人数统计 (10 分)

import java.util.Scanner;


public class Main {

	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		int n=in.nextInt();
		int a=0,b=0;
		for(int i=0;i<n;i++) {
			int x=in.nextInt();
			try {
				if(x>100||x<0) throw new Exception(x+"invalid!");
				else if(x>=60)a++;
				else b++;
			}
			catch (Exception e) {
				i--;
				System.out.println(e.getMessage());
			}
		}
		System.out.println(a);
		System.out.println(b);
	}
}

7-20 jmu-Java-02基本语法-02-StringBuilder (10 分)

import java.util.Scanner;
import java.text.DecimalFormat;

public class Main {
    public static void main(String[] args) {
    	Scanner in =new Scanner(System.in);
    	
    	while(in.hasNextInt()) {
    		int n,begin,end;
    		n=in.nextInt();
    		begin=in.nextInt();
    		end=in.nextInt();
    		StringBuilder s =new StringBuilder();
    		for(int i=0;i<n;i++) {
    			s.append(i);
    		}
    		System.out.println(s.substring(begin, end));
    	}
    } 
}

7-21 单词替换 (20 分)

import java.util.Scanner;


public class Main{
    public static void main(String[] args) {
         Scanner in = new Scanner(System.in);
         String s=new String(),a,b;
         s=in.nextLine();
         a=in.next();
         b=in.next();
         String[] arr=s.split("\\s+");
         StringBuilder ans=new StringBuilder();
         for(int i=0;i<arr.length;i++) {
        	 if(arr[i].equals(a))ans.append(b);
        	 else ans.append(arr[i]);
        	 if(i!=arr.length-1)ans.append(" ");
         }
         System.out.println(ans);
    }
}

7-22 jmu-java-随机数-使用蒙特卡罗法计算圆周率的值 (10 分)

import java.util.*;
public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner in = new Scanner(System.in);
		long seed = in.nextLong();
        int n = in.nextInt();
		Random r = new Random(seed);
		int count = 0;
		for (int i=0;i<n;i++) {
			double x = r.nextDouble()*2-1;
			double y = r.nextDouble()*2-1;
			if ( x*x + y*y <=1) count++;
		}
		System.out.println(4*(double)count/n);	
	}
}

7-23 通过键盘输入一行字符，分别统计出其中英文字母、空格、数字和其它字符的个数。 (10 分)

import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String str = sc.nextLine();
		sc.close();
		
		char[] chars = str.toCharArray();
		int letter=0,num=0,blank=0,other=0;
		for(int i=0;i<chars.length;i++) {
			if((chars[i]>='A' && chars[i]<='Z') || (chars[i]>='a' && chars[i]<='z')){
				letter++;
			}else if(chars[i]>=47 && chars[i]<=57) {
				num++;
			}else if(chars[i]==32) {
				blank++;
			}else {
				other++;
			}
		}
		
		System.out.println("字母个数："+letter);
		System.out.println("数字个数："+num);
		System.out.println("空格个数："+blank);
		System.out.println("其他字符个数："+other);
	}
}

7-24 jmu-Java-02基本语法-08-ArrayList入门 (10 分)

import java.util.*;
public class Main {

	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		ArrayList <String> vector=new ArrayList<String> ();
		String s;
		while(true) {
			s=in.next();
			if(s.equals("!!end!!"))break;
			vector.add(s);
		}
		vector.add("end");
		vector.add(0,"begin");
		System.out.println(vector);
		s=in.next();
		if(vector.contains(s))System.out.println("true"+"\n"+vector.indexOf(s));
		else System.out.println("false"+"\n"+"-1");
		System.out.println(vector.lastIndexOf(s));
        System.out.println(vector.get(0));
		vector.remove(0);
		System.out.println(vector);
		s=in.next();
		vector.set(1, s);
		System.out.println(vector);
		s=in.next();
		ArrayList<String> list=new ArrayList<String>();
		for(String i: vector) {
			if(i.contains(s))list.add(i);
		}
		System.out.println(list);
		if(vector.contains(s))vector.remove(vector.indexOf(s));
		System.out.println(vector);
		vector.clear();
		System.out.println(vector+","+vector.size()+","+vector.isEmpty());
		
	}
}

7-25 找到出勤最多的人 (10 分)

import java.util.*;
public class Main {

	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		Map<String, Integer> ma =new HashMap<String, Integer>();
		String s;
		int max=0;
		ArrayList<String> ans=new ArrayList<String>();
		while(in.hasNext()) {
			s=in.next();
			Integer vis=ma.get(s);
			vis=vis==null?1:vis+1;
			ma.put(s, vis);
			if(vis>max) {
				max=vis;
				ans.clear();
				ans.add(s);
			}
			else if(vis==max) {
				ans.add(s);
			}
		}
		int cou=0;
		for(String i: ans) {
			cou++;
			System.out.println(i);
			if(cou!=ans.size())System.out.println(" ");
		}
	}
}

7-26 创建一个倒数计数线程 (10 分)

import java.util.*;

class Task implements Runnable{
	int n;
	Task(int n){
		this.n=n;
	}
	@Override
	public void run() {
		// TODO Auto-generated method stub
		for(int i=n;i>=0;i--) {
			int time=500;
			while(time-->0);
			System.out.println(i);
		}
	}
	
}

public class Main {

	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		int n = in.nextInt();
		Thread t = new Thread(new Task(n));
        t.start();
	}
}

7-27 程序改错题4 (5 分)

import java.util.*;

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Thread t = new Thread(new RunHandler());
        t.run();
    }
}

class RunHandler implements Runnable{
    public void run() {
        Scanner in = new Scanner(System.in);
        int x = in.nextInt();
        while(x-->0)
            System.out.println("run");
    }
}

7-28 USB接口的定义 (10 分)

import java.util.*;

interface USB{
	public abstract void work();
	public abstract void stop();
}

class Mouse implements USB{
	
	@Override
	public void stop() {
		// TODO Auto-generated method stub
		System.out.println("我不能点了");
	}
	@Override
	public void work() {
		// TODO Auto-generated method stub
		System.out.println("我点点点");
	}
}

class UPan implements USB{
	@Override
	public void work() {
		// TODO Auto-generated method stub
		System.out.println("我存存存");
	}
	@Override
	public void stop() {
		// TODO Auto-generated method stub
		System.out.println("我走了");
	}
}

public class Main {
    public static void main(String[] args) {
       USB usb1 =new Mouse();
       usb1.work();
       usb1.stop();
       USB usb[]=new USB[6];
       usb[0]=new UPan();
       usb[1]=new Mouse();
       for(USB i: usb) {
    	   i.work();
    	   i.stop();
       }
    }
}

7-29 Circle类 (10 分)

import java.util.*;

class Circle{
	private int r;
	public Circle(){
		this.r=2;
		System.out.println("this is a constructor");
	}
	public Circle(int r){
		if(r<=0)this.r=2;
		else this.r=r;
		System.out.println("this is a constructor with para");
	}
	public int get() {
		return r;
	}
	public void set(int r) {
		if(r<=0) this.r=2;
		else this.r = r;
	}
	public int getArea() {
		return (int)(Math.PI*r*r);
	}
	@Override
	public String toString() {
		return "Circle [radius=" + r + "]";
	}
}

public class Main {

	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		Circle c1 =new Circle();
		System.out.println(c1);
		System.out.println("c1:area="+c1.getArea());
		Circle c2 = new Circle();
		System.out.println(c2);
		int r=in.nextInt();
		c2.set(r);
		System.out.println(c2);
		System.out.println("c2:area="+c2.getArea());
		Circle c3 =new Circle(in.nextInt());
		System.out.println(c3);
		System.out.println("c3:area="+c3.getArea());
	}
}

7-30 数组与对象 (10 分)

import java.util.*;

import org.omg.PortableInterceptor.NON_EXISTENT;

class Person{
	String name;
	public Person(){
		this.name="none";
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public Person(String name) {
		this.name=name;
	}
	public String toString(){ return "name:"+name; }
}

public class Main {
    public static void main(String[] args) {
    	Scanner in =new Scanner(System.in);
    	Person a[]=new Person[2];
    	a[0]=new Person();
    	a[1]=new Person(in.next());
    	for(Person i: a) {
    		System.out.println(i);
    	}
    }
}

7-31 圆柱体类设计 (10 分)

import java.util.*;

import org.omg.PortableInterceptor.NON_EXISTENT;

class Yz{
	int r,h;
	public Yz() {
		this(2,1);
		System.out.println("Constructor no para");
	}
	public Yz(int r,int h) {
		this.r=r;
		this.h=h;
		System.out.println("Constructor with para");
	}
	public int getV(){
		return (int)(Math.PI*r*r*h);
	}
	public int getR() {
		return r;
	}

	public void setR(int r) {
		this.r = r;
	}

	public int getH() {
		return h;
	}

	public void setH(int h) {
		this.h = h;
	}
	
}

public class Main {
    public static void main(String[] args) {
    	Scanner in = new Scanner(System.in);
    	int r=in.nextInt();
    	int h=in.nextInt();
    	Yz c1=new Yz(r,h);
    	System.out.println(c1.getV());
    	Yz c2=new Yz();
    	System.out.println(c2.getV());
    }
}

7-32 List的使用 (15 分)

import java.util.*;

import org.omg.PortableInterceptor.NON_EXISTENT;

class Person{
	String name;
	int age;
	public Person() {
		
	}
	public Person(String name,int age) {
		this.name=name;
		this.age=age;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	@Override
	public String toString() {
		return "Person [name=" + name + ", age=" + age + "]";
	}
	
}

public class Main {
    public static void main(String[] args) {
    	Scanner in = new Scanner(System.in);
    	List <Person> list =new ArrayList<Person>();
    	int n=in.nextInt();
    	while(n-->0) {
    		list.add(new Person(in.next(),in.nextInt()));
    	}
    	for(Person i: list) {
    		System.out.println(i);
    	}
    	String name=in.next();
    	boolean flag=true;
    	for(Person i: list) {
    		if(i.name.equals(name)) {
    			System.out.println(i);
    			flag=false;
    			break;
    		}
    	}
    	if(flag) System.out.println("此人不存在");
    }
}

7-33 jmu-Java-03面向对象基础-03-形状 (10 分)

import java.util.Arrays;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Rectangle[] rectangle = new Rectangle[2];
		Circle[] circle = new Circle[2];
		Scanner sc = new Scanner(System.in);
		for(int i=0;i<rectangle.length;i++) {
			rectangle[i] = new Rectangle(sc.nextInt(),sc.nextInt());
		}
		for(int i=0;i<circle.length;i++) {
			circle[i] = new Circle(sc.nextInt());
		}
		System.out.println(rectangle[0].getPerimeter()+rectangle[1].getPerimeter()+
				circle[0].getPerimeter()+circle[1].getPerimeter());
		System.out.println(rectangle[0].getArea()+rectangle[1].getArea()+
				circle[0].getArea()+circle[1].getArea());
		System.out.println(Arrays.deepToString(rectangle));
		System.out.println(Arrays.deepToString(circle));
		sc.close();
	}
}


class Rectangle{
	private int width;
	private int length;
	
	public Rectangle(int width,int length) {
		this.width = width;
		this.length = length;
	}
	
//求周长方法
	public int getPerimeter() {
		return 2*(width+length);
	}
//求面积方法
	public int getArea() {
		return width*length;
	}

	@Override
	public String toString() {
		return "Rectangle [width=" + width + ", length=" + length + "]";
	}
	
}


class Circle{
	private int radius;
	
	public Circle(int radius) {
		this.radius = radius;
	}
	
//求周长方法
	public int getPerimeter() {
		return (int)(2*Math.PI*radius);
	}
//求面积方法
	public int getArea() {
		return (int)(Math.PI*radius*radius);
	}

	@Override
	public String toString() {
		return "Circle [radius=" + radius + "]";
	}
	
}