【java】第9章对象和类测试题（作业部分）

落日映苍穹つ 2022-10-21 14:53 193阅读 0赞

### 文章目录 ###

*   *  9.1
     *  9.4
     *  9.5
     *  9.9
     *  9.12
     *  9.13

## 9.1 ##

![在这里插入图片描述][202105051601272.png]  
![在这里插入图片描述][20210505160149443.png]

package wwr;
    //9.1
    class Rectangle {
        
    	//宽&高
    	double width;	
    	double height;
    	//无参构造
    	Rectangle() {
        
    		width = 1;
    		height = 1;
    	}
    	//构造方法
    	Rectangle(double newWidth, double newHeight) {
        
    		width = newWidth;
    		height = newHeight;
    	}
    	//面积
    	double getArea() {
        
    		return width * height;
    	}
    	//周长
    	double getPerimeter() {
        
    		return 2 * (width + height);
    	}
    }
    public class Demo {
        
    	
        public static void main(String[] args) {
        
            Rectangle rectangle1 = new Rectangle(4, 40);
            System.out.println("The width of rectangle1 is " + rectangle1.width);
            System.out.println("The height of rectangle1 is " + rectangle1.height);
            System.out.println("The area of rectangle1 is " + rectangle1.getArea());
            System.out.println("The perimeterof rectangle1 is " + rectangle1.getPerimeter());
            Rectangle rectangle2 = new Rectangle(3.5, 35.9);
            System.out.println("The width of rectangle2 is " + rectangle2.width);
            System.out.println("The height of rectangle2 is " + rectangle2.height);
            System.out.println("The area of rectangle2 is " + rectangle2.getArea());
            System.out.println("The perimeterof rectangle2 is " + rectangle2.getPerimeter());
    
        }
    }

## 9.4 ##

![在这里插入图片描述][20210505160238390.png]

package wwr;
    //9.4
    import java.util.Random;
    public class Demo {
        
    	
        public static void main(String[] args) {
        
            
        	Random random = new java.util.Random(1000);
        	for(int i = 0; i < 50; i++) {
        
        		System.out.print(random.nextInt(100) + " ");
        	}
        }
    }

## 9.5 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQ1ODc4Mjky_size_16_color_FFFFFF_t_70]

package wwr;
    //9.5
    import java.util.GregorianCalendar;
    public class Demo {
        
    	
        public static void main(String[] args) {
        
            
        	GregorianCalendar calendar = new GregorianCalendar();
        	System.out.print(calendar.get(GregorianCalendar.YEAR) + 
        			//月份是从0开的，比如1月输出0，所以都得加1，好坑QAQ
        			" " + (calendar.get(GregorianCalendar.MONTH) + 1) +
        			" " + calendar.get(GregorianCalendar.DAY_OF_MONTH));
        	System.out.println();
        	calendar.setTimeInMillis(1234567898765L);
        	System.out.print(calendar.get(GregorianCalendar.YEAR) + 
        			" " + (calendar.get(GregorianCalendar.MONTH) + 1) + 
        			" " + calendar.get(GregorianCalendar.DAY_OF_MONTH));
        }
    }

## 9.9 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQ1ODc4Mjky_size_16_color_FFFFFF_t_70 1]  
![在这里插入图片描述][20210505160354926.png]

package wwr;
    //9.9
     class RegularPolygon {
        
    	 
    	private int n;			//边数
    	private double side; 	//边长
    	private double x;		//中点x坐标	
    	private double y;		//中点y坐标
    	//带有默认值的无参构造
    	RegularPolygon() {
        
    		n = 3;
    		side = 1;
    		x = 0;
    		y = 0;
    	}
    	//指定边数和边长，中心在(0, 0)
    	RegularPolygon(int newN, double newSide) {
        
    		n = newN;
    		side = newSide;
    		x = 0;
    		y = 0;
    	}
    	//指定边数和边长，中心在(x, y)
    	RegularPolygon(int newN, double newSide, double newX, double newY) {
        
    		n = newN;
    		side = newSide;
    		x = newX;
    		y = newY;
    	}
    	//访问器
    	int getN() {
        
    		return n;
    	}
    	double getSide() {
        
    		return side;
    	}
    	double getX() {
        
    		return x;
    	}
    	double getY() {
        
    		return y;
    	}
    	//修改器
    	void setN(int newN) {
        
    		n = newN;
    	}
    	void setSide(double newSide) {
        
    		side = newSide;
    	}
    	void setX(double newX) {
        
    		x = newX;
    	}
    	void setY(double newY) {
        
    		y = newY;
    	}
    	//周长
    	double getPerimeter() {
        
    		return side * n;
    	}
    	//面积
    	double getArea() {
        
    		return (n * side * side) / (4 * Math.tan(Math.PI / n));
    	}
    }
    
    public class Demo {
        
    	
        public static void main(String[] args) {
        
            
        	RegularPolygon rp1 = new RegularPolygon();
        	RegularPolygon rp2 = new RegularPolygon(6, 4);
        	RegularPolygon rp3 = new RegularPolygon(10, 4, 5.6, 7.8);
        	System.out.println("rp1's perimeter is " + 
        			rp1.getPerimeter() + ", rp1's area is " + rp1.getArea());
        	System.out.println("rp2's perimeter is " + 
        	    	rp2.getPerimeter() + ", rp2's area is " + rp2.getArea());
        	System.out.println("rp3's perimeter is " + 
        	    	rp3.getPerimeter() + ", rp3's area is " + rp3.getArea());
        }
    }

## 9.12 ##

![在这里插入图片描述][20210505160439251.png]

package wwr;
    //9.12
    import java.util.Scanner;
    class LinearEquation {
        
    	
    	private double a;
    	private double b;
    	private double c;
    	private double d;
    	private double e;
    	private double f;
    	
    	LinearEquation(double a, double b, double c, double d, double e, double f) {
        
    		this.a = a;
    		this.b = b;
    		this.c = c;
    		this.d = d;
    		this.e = e;
    		this.f = f;
    	}
    	
    	double getA() {
        
    		return a;
    	}
    	double getB() {
        
    		return b;
    	}
    	double getC() {
        
    		return c;
    	}
    	double getD() {
        
    		return d;
    	}
    	double getE() {
        
    		return e;
    	}
    	double getF() {
        
    		return f;
    	}
    	double getX() {
        
    		return (e * d - b * f) / (a * d - b * c) ;
    	}
    	double getY() {
        
    		return (a * f - e * c) / (a * d - b * c);
    	}
    	
    }
    public class Demo {
        
    	
        public static void main(String[] args) {
        
            
        	Scanner input = new Scanner(System.in);
        	System.out.print("Enter the two endpoints of the first line segment (x1, y1, x2, y2): ");
        	double x1 = input.nextInt();
        	double y1 = input.nextInt();
        	double x2 = input.nextInt();
        	double y2 = input.nextInt();
        	double a = (y1 - y2) / (x2 - x1);
        	double b = 1;
        	double e = y1 - ((x1 * (y2 - y1)) / (x2 - x1));
        	System.out.print("Enter the two endpoints of the second line segment (x3, y3, x4, y4): ");
        	double x3 = input.nextInt();
        	double y3 = input.nextInt();
        	double x4 = input.nextInt();
        	double y4 = input.nextInt();
        	double c = (y3 - y4) / (x4 - x3);
        	double d = 1;
        	double f = y3 - ((x3 * (y4 - y3)) / (x4 - x3));
        	if(a * d - b * c == 0)
        		System.out.println("The equation has no solution");
        	else {
        
        		LinearEquation le = new LinearEquation(a, b, c, d, e, f);
    //			LinearEquation le = new LinearEquation(9.0, 4.0, 3.0, -5.0, -6.0, -21.0);
    			double tepX = le.getX();
    			double tepY = le.getY();
    			System.out.print("x is " + tepX + " and y is " + tepY);
        	}
        }
    }

## 9.13 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQ1ODc4Mjky_size_16_color_FFFFFF_t_70 2]

package wwr;
    //9.13
    import java.util.Scanner;
    
    class Location {
        
    	
    	public int row;
    	public int column;
    	public double maxValue;
    	public static Location locateLargest(double[][] a) {
        
    		Location lo = new Location();
    		lo.maxValue = a[0][0];
    		for(int i = 0; i < a.length; i++)
    			for(int j = 0; j < a[0].length; j++ )
    				if(a[i][j] > lo.maxValue) {
        
    					lo.maxValue = a[i][j];
    					lo.row = i;
    					lo.column = j;
    				}
    		return lo;
    	}
    }
    public class Demo {
        
    	
        public static void main(String[] args) {
        
            
        	Scanner input = new Scanner(System.in);
        	System.out.print("Enter the number of rows and columns in the array: ");
        	int Row = input.nextInt();
        	int Column = input.nextInt();
        	System.out.println("Enter the array: ");
        	double array[][] = new double[Row + 2][Column + 2];
        	for(int i = 0; i < Row; i++)
        		for(int j = 0; j < Column; j++)
        			array[i][j] = input.nextDouble();
        	Location LO = new Location();
        	LO = LO.locateLargest(array);
        	System.out.print("The location of the largest element is " + LO.maxValue 
        			+ " at (" + LO.row + ", " + LO.column + ")");
        }
        
    }

[202105051601272.png]: /images/20221021/1c3a23cb09bb4686ac954f21dfa0c7f2.png
[20210505160149443.png]: /images/20221021/fe0a5dabf0074dd68ed9fd1a7b00ea6a.png
[20210505160238390.png]: /images/20221021/eff02b0222c64d38b85cab99dc1ef9f7.png
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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQ1ODc4Mjky_size_16_color_FFFFFF_t_70 1]: /images/20221021/88d71446abe3496e89427f26597c8a6e.png
[20210505160354926.png]: /images/20221021/94bb2832ea504126b0ffc0074e80a4af.png
[20210505160439251.png]: /images/20221021/640169e1b86f425ba8f722c80c813058.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQ1ODc4Mjky_size_16_color_FFFFFF_t_70 2]: /images/20221021/684ce89a303742b4a04140b11a3bda39.png