public class Sample{private int x; private Sample(){x=1; }public void Sample(double f){this.x = (int)f; }public Sample(String s){}}共有多少个构造方法
时间: 2024-01-29 13:02:08 浏览: 35
在这个类中,共有 3 个构造方法。它们分别是:
1. 无参构造方法 `private Sample()`,用于初始化对象的 `x` 成员变量为 1。
2. 带有一个 `double` 类型参数的构造方法 `public void Sample(double f)`,用于将传入的 `double` 类型参数转换成 `int` 类型,并赋值给对象的 `x` 成员变量。
3. 带有一个 `String` 类型参数的构造方法 `public Sample(String s)`,没有实现内容。
需要注意的是,第一个构造方法是私有的,只能在类内部被调用,不能在类外部被调用。而另外两个构造方法是公有的,可以在类外部被调用。通过提供不同数量或类型的构造方法,可以方便地创建对象并初始化对象的状态,增强了代码的灵活性和可维护性。
相关问题
使用java完成下列任务1. Read the sample code listing 5.1 to 5.3 of Core Java. 2. Implement a class of Person including fields of id, name, gender, age, and the methods to access these fields as well as a desciption function. 3. Implement a class of Student that inherits the Person class by adding additional fields of major and gpa. In addition, the methods include the accessors to get all the fields, respectively. 4. Rewrite the description function, and test it using three kinds of initializations.
Sure, I can help you with that. Here is the solution to your problem:
1. Sample code listing 5.1 to 5.3 of Core Java:
```
//listing 5.1
public class Manager extends Employee {
private double bonus;
public Manager(String name, double salary, int year, int month, int day) {
super(name, salary, year, month, day);
bonus = 0;
}
public double getSalary() {
double baseSalary = super.getSalary();
return baseSalary + bonus;
}
public void setBonus(double bonus) {
this.bonus = bonus;
}
}
//listing 5.2
public class Employee {
private String name;
private double salary;
private LocalDate hireDay;
public Employee(String name, double salary, int year, int month, int day) {
this.name = name;
this.salary = salary;
hireDay = LocalDate.of(year, month, day);
}
public String getName() {
return name;
}
public double getSalary() {
return salary;
}
public LocalDate getHireDay() {
return hireDay;
}
public void raiseSalary(double byPercent) {
double raise = salary * byPercent / 100;
salary += raise;
}
}
//listing 5.3
public class ManagerTest {
public static void main(String[] args) {
Manager boss = new Manager("Carl Cracker", 80000, 1987, 12, 15);
boss.setBonus(5000);
Employee[] staff = new Employee[3];
staff[0] = boss;
staff[1] = new Employee("Harry Hacker", 50000, 1989, 10, 1);
staff[2] = new Employee("Tommy Tester", 40000, 1990, 3, 15);
for (Employee e : staff) {
System.out.println("name=" + e.getName() + ",salary=" + e.getSalary());
}
}
}
```
2. Implementation of a class of Person including fields of id, name, gender, age, and the methods to access these fields as well as a description function:
```
public class Person {
private int id;
private String name;
private String gender;
private int age;
public Person(int id, String name, String gender, int age) {
this.id = id;
this.name = name;
this.gender = gender;
this.age = age;
}
public int getId() {
return id;
}
public String getName() {
return name;
}
public String getGender() {
return gender;
}
public int getAge() {
return age;
}
public String getDescription() {
return "ID: " + id + ", Name: " + name + ", Gender: " + gender + ", Age: " + age;
}
}
```
3. Implementation of a class of Student that inherits the Person class by adding additional fields of major and gpa. In addition, the methods include the accessors to get all the fields, respectively:
```
public class Student extends Person {
private String major;
private double gpa;
public Student(int id, String name, String gender, int age, String major, double gpa) {
super(id, name, gender, age);
this.major = major;
this.gpa = gpa;
}
public String getMajor() {
return major;
}
public double getGpa() {
return gpa;
}
public String getDescription() {
return super.getDescription() + ", Major: " + major + ", GPA: " + gpa;
}
}
```
4. Rewrite the description function, and test it using three kinds of initializations:
```
public static void main(String[] args) {
// initialization 1
Person person1 = new Person(1, "John", "Male", 30);
System.out.println(person1.getDescription());
// initialization 2
Person person2 = new Person(2, "Jane", "Female", 25);
System.out.println(person2.getDescription());
// initialization 3
Student student1 = new Student(3, "Mike", "Male", 20, "Computer Science", 3.8);
System.out.println(student1.getDescription());
}
```
Output:
```
ID: 1, Name: John, Gender: Male, Age: 30
ID: 2, Name: Jane, Gender: Female, Age: 25
ID: 3, Name: Mike, Gender: Male, Age: 20, Major: Computer Science, GPA: 3.8
```
I hope this solution helps you. Let me know if you have any questions or need further assistance.
用Java写x(t)=-2tsin(t2),0≤t≤8,从0开始,以△t=0.01、0.02、0.04、0.08、0.1、0.25、0.5、1等为间隔,分别绘制不同△t下的x(t)的离散曲线
好的,您可以使用以下的Java代码来绘制不同△t下的x(t)的离散曲线:
```
import javax.swing.*;
import java.awt.*;
public class DiscretePlot extends JPanel {
private double[] xValues; // 存储x值的数组
private double[] tValues; // 存储t值的数组
private double deltaT; // △t的值
private int nPoints; // 计算出的点数
private int sampleRate; // 绘图的采样率
public DiscretePlot(double deltaT, int sampleRate) {
this.deltaT = deltaT;
this.nPoints = (int) Math.ceil(8 / deltaT); // 计算出的点数
this.xValues = new double[nPoints];
this.tValues = new double[nPoints];
this.sampleRate = sampleRate;
// 计算x(t)和t的离散值
for (int i = 0; i < nPoints; i++) {
tValues[i] = i * deltaT;
xValues[i] = -2 * tValues[i] * Math.sin(tValues[i] * tValues[i]);
}
}
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
// 设置画笔
Graphics2D g2d = (Graphics2D) g;
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2d.setColor(Color.BLACK);
g2d.setStroke(new BasicStroke(2));
// 绘制x(t)的离散曲线
for (int i = 0; i < nPoints - 1; i++) {
int x1 = (int) Math.round(tValues[i] * sampleRate);
int y1 = (int) Math.round(xValues[i] * sampleRate);
int x2 = (int) Math.round(tValues[i + 1] * sampleRate);
int y2 = (int) Math.round(xValues[i + 1] * sampleRate);
g2d.drawLine(x1, getHeight() - y1, x2, getHeight() - y2); // 使用getHeight() - y是为了将坐标系上移,使其原点在左下角
}
}
public static void main(String[] args) {
JFrame f = new JFrame();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setSize(800, 600);
JPanel p = new JPanel(new GridLayout(1, 0));
p.add(new DiscretePlot(0.01, 40));
p.add(new DiscretePlot(0.02, 20));
p.add(new DiscretePlot(0.04, 10));
p.add(new DiscretePlot(0.08, 5));
p.add(new DiscretePlot(0.1, 4));
p.add(new DiscretePlot(0.25, 2));
p.add(new DiscretePlot(0.5, 1));
p.add(new DiscretePlot(1, 1));
f.add(p);
f.setVisible(true);
}
}
```
在上述代码中,我们定义了一个`DiscretePlot`类,其构造方法需要传入△t的值和绘图的采样率。在构造方法中,我们计算出了x(t)和t的离散值,并保存在数组`xValues`和`tValues`中。在`paintComponent`方法中,我们使用Graphics2D的`drawLine`方法绘制了离散曲线。最后,在main方法中,我们创建了多个`DiscretePlot`实例,并添加到了一个JPanel中,然后将这个JPanel添加到了JFrame中。
您可以自行运行上述代码,然后观察不同△t下的x(t)的离散曲线。
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