Java优学网构造方法入门解析：轻松掌握对象创建与初始化技巧

public class Student {

private String name;
private int age;

// 这是一个构造方法
public Student(String studentName, int studentAge) {
    name = studentName;
    age = studentAge;
}

}

public class Book {

private String title;
// 编译器会自动添加：public Book() { super(); }

}

public class Student {

private String name;
private int age;

public Student(String name, int age) {
    this.name = name;  // this.name指实例变量，name指参数
    this.age = age;
}

}

public class Product {

public Product() {
    // 任何包的任何类都能创建Product对象
}

}

public class Employee {

private String name;
private int age;
private String department;

public Employee(String name) {
    this(name, 0);
}

public Employee(String name, int age) {
    this(name, age, "未分配");
}

public Employee(String name, int age, String department) {
    this.name = name;
    this.age = age;
    this.department = department;
}

}

// 推荐的做法 public class User {

private String username;
private String email;

public User(String username, String email) {
    this.username = validateUsername(username);
    this.email = validateEmail(email);
}

private String validateUsername(String username) {
    if (username == null || username.trim().isEmpty()) {
        throw new IllegalArgumentException("用户名不能为空");
    }
    return username.trim();
}

}