构造完之后，重载有什莫用

public class Loan {
private double annualInterestRate;
private int numberOfYears;
private double loanAmount;
private Date loanDate;

public Loan() {
    this(2.5, 1, 1000);
}

public Loan(double annualInterestRate, int numberOfYears, 
        double loanAmount) {
    this.annualInterestRate = annualInterestRate;
    this.numberOfYears = numberOfYears;
    this.loanAmount = loanAmount;
    loanDate = new Date();
    
 }

}
public Loan(){}方法有什么用。

默认构造函数一般还是需要的，比如将Load类对象作为参数时，就会自动调用默认构造函数。
有参构造函数可用于有初始化参数的构造场景
本文代码的默认构造函数调用了有参构造函数，提供了默认的成员变量值进行初始化

这是无参构造函数，比如你new Loan()，它会帮你创建一个Loan(2.5,1,1000)，就是起到一个默认参数的作用