实验名称 实验二 类与对象
实验目的
1. 深刻理解类的封装与继承;
2. 熟练掌握类的定义、包与路径、对象的创建、方法的调用、类的继承、方法的重写、运行时多态、访问权限修饰符的使用等;
3. 熟练运用JDK提供的常用类及API。
实验内容(4学时)
1. 定义一个圆形类Circle,包括:
(1)属性:圆心、半径
(2)方法:求面积、周长;上下左右平移;缩放;绘图(虚拟表示)。
设计测试类CircleDemo,在测试类中测试上述方法。以后实验中均自行设计测试类。
class Circle {private double centerX;private double centerY;private double radius;public Circle(double centerX, double centerY, double radius) {this.centerX = centerX;this.centerY = centerY;this.radius = radius;}public double getArea() {return Math.PI * radius * radius;}public double getPerimeter() {return 2 * Math.PI * radius;}public void translate(double deltaX, double deltaY) {centerX += deltaX;centerY += deltaY;}public void scale(double factor) {radius *= factor;}public void draw() {System.out.println("Drawing a circle at (" + centerX + ", " + centerY + ") with radius " + radius);}
}public class CircleDemo {public static void main(String[] args) {Circle circle = new Circle(0, 0, 5.0);System.out.println("Area: " + circle.getArea());System.out.println("Perimeter: " + circle.getPerimeter());circle.translate(2.0, 3.0);circle.scale(1.5);circle.draw();}
}
2. 设计Bird类,包括:(1)属性:name;(2)方法:fly( ),fly方法以及后面提到的各种方法均以字符串输出来演示功能。
以Bird类为超类(父类),设计子类CarrierPigeon,
(1)为CarrierPigeon类新增方法:send(String address, String message)
(2)在CarrierPigeon 覆盖 Bird 的 fly() 方法
public class Bird {private String name;public Bird(String name) {this.name = name;}public String getName() {return name;}public void fly() {System.out.println(name + " is flying.");}
}public class CarrierPigeon extends Bird {public CarrierPigeon(String name) {super(name);}public void send(String address, String message) {System.out.println(getName() + " is sending a message to " + address + ": " + message);}@Overridepublic void fly() {System.out.println(getName() + " is flying with a message.");}
}public class BirdDemo {public static void main(String[] args) {Bird bird = new Bird("Sparrow");bird.fly();CarrierPigeon pigeon = new CarrierPigeon("Pigeon");pigeon.fly();pigeon.send("Recipient", "Important message");}
}
3. Java编程实现:设计复数类Complex,类中实部和虚部都是实数,实现加法、减法、乘法和除法。
public class Complex {private double real;private double imaginary;public Complex(double real, double imaginary) {this.real = real;this.imaginary = imaginary;}public Complex add(Complex other) {double newReal = this.real + other.real;double newImaginary = this.imaginary + other.imaginary;return new Complex(newReal, newImaginary);}public Complex subtract(Complex other) {double newReal = this.real - other.real;double newImaginary = this.imaginary - other.imaginary;return new Complex(newReal, newImaginary);}public Complex multiply(Complex other) {double newReal = this.real * other.real - this.imaginary * other.imaginary;double newImaginary = this.real * other.imaginary + this.imaginary * other.real;return new Complex(newReal, newImaginary);}public Complex divide(Complex other) {double denominator = other.real * other.real + other.imaginary * other.imaginary;double newReal = (this.real * other.real + this.imaginary * other.imaginary) / denominator;double newImaginary = (this.imaginary * other.real - this.real * other.imaginary) / denominator;return new Complex(newReal, newImaginary);}@Overridepublic String toString() {return real + " + " + imaginary + "i";}
}public class ComplexDemo {public static void main(String[] args) {Complex c1 = new Complex(2.0, 3.0);Complex c2 = new Complex(1.0, 1.0);Complex sum = c1.add(c2);Complex difference = c1.subtract(c2);Complex product = c1.multiply(c2);Complex quotient = c1.divide(c2);System.out.println("Sum: " + sum);System.out.println("Difference: " + difference);System.out.println("Product: " + product);System.out.println("Quotient: " + quotient);}
}
4. Java编程实现:设计矩阵类Matrix,类中的方法能对矩阵进行加法、减法和乘法运算。在矩阵中再定义一个方法,生成如下的矩阵:
public class Matrix {private int[][] data;public Matrix(int[][] data) {this.data = data;}// 获取矩阵的行数public int getRows() {return data.length;}// 获取矩阵的列数public int getColumns() {return data[0].length;}// 矩阵加法public Matrix add(Matrix other) {if (getRows() != other.getRows() || getColumns() != other.getColumns()) {throw new IllegalArgumentException("矩阵维度不匹配");}int[][] result = new int[getRows()][getColumns()];for (int i = 0; i < getRows(); i++) {for (int j = 0; j < getColumns(); j++) {result[i][j] = data[i][j] + other.data[i][j];}}return new Matrix(result);}// 矩阵减法public Matrix subtract(Matrix other) {if (getRows() != other.getRows() || getColumns() != other.getColumns()) {throw new IllegalArgumentException("矩阵维度不匹配");}int[][] result = new int[getRows()][getColumns()];for (int i = 0; i < getRows(); i++) {for (int j = 0; j < getColumns(); j++) {result[i][j] = data[i][j] - other.data[i][j];}}return new Matrix(result);}// 矩阵乘法public Matrix multiply(Matrix other) {if (getColumns() != other.getRows()) {throw new IllegalArgumentException("矩阵维度不匹配");}int[][] result = new int[getRows()][other.getColumns()];for (int i = 0; i < getRows(); i++) {for (int j = 0; j < other.getColumns(); j++) {int sum = 0;for (int k = 0; k < getColumns(); k++) {sum += data[i][k] * other.data[k][j];}result[i][j] = sum;}}return new Matrix(result);}// 生成指定的矩阵public static Matrix createMatrixE() {int[][] eMatrixData = {{1, 3, 8, 7, 5, 6},{3, 8, 7, 5, 6, 1},{8, 7, 5, 6, 1, 3},{7, 5, 6, 1, 3, 8},{5, 6, 1, 3, 8, 7},{6, 1, 3, 8, 7, 5}};return new Matrix(eMatrixData);}// 打印矩阵public void printMatrix() {for (int i = 0; i < getRows(); i++) {for (int j = 0; j < getColumns(); j++) {System.out.print(data[i][j] + " ");}System.out.println();}}public static void main(String[] args) {Matrix matrixE = createMatrixE();System.out.println("Matrix E:");matrixE.printMatrix();Matrix matrixA = new Matrix(new int[][] {{1, 2, 3},{4, 5, 6},{7, 8, 9}});Matrix matrixB = new Matrix(new int[][] {{9, 8, 7},{6, 5, 4},{3, 2, 1}});System.out.println("\nMatrix A:");matrixA.printMatrix();System.out.println("\nMatrix B:");matrixB.printMatrix();Matrix matrixSum = matrixA.add(matrixB);System.out.println("\nMatrix A + B:");matrixSum.printMatrix();Matrix matrixDifference = matrixA.subtract(matrixB);System.out.println("\nMatrix A - B:");matrixDifference.printMatrix();Matrix matrixProduct = matrixA.multiply(matrixB);System.out.println("\nMatrix A * B:");matrixProduct.printMatrix();}
}
实验程序及结果(附录)
思考
以C为代表的结构化编程语言和以Java为代表的面向对象编程语言有哪些本质不同?
关于结构化编程语言(以C为代表)和面向对象编程语言(以Java为代表)的本质不同:
- 抽象与封装:面向对象编程强调对象的抽象和封装,允许将数据和操作封装在对象内部,提供更好的信息隐藏和模块化。结构化编程相对较少使用对象,更多地依赖于函数和数据的分离。
- 继承与多态:面向对象编程支持继承和多态,允许创建层次结构的类,重用代码并实现多态性。结构化编程通常较少使用这些概念,更注重逻辑流程和模块化设计。
- 对象:面向对象编程以对象为中心,将数据和操作封装在对象中。结构化编程更倾向于使用数据结构和函数。
- 设计模式:面向对象编程强调设计模式,例如单例模式、工厂模式等,以提供更好的可维护性和可扩展性。结构化编程通常较少使用这些模式。
- 类型系统:面向对象编程通常有更强的类型系统,支持多态和动态绑定。结构化编程的类型系统通常较为简单。
总之,面向对象编程更注重数据和操作的封装、继承、多态等概念,而结构化编程更注重逻辑流程和分离数据和函数。不同编程范式适用于不同类型的问题和项目。