java - 修复覆盖错误

Question

我尝试运行一个程序，但出现这四个错误。

TestCusomer.java:25: error: toString() in Invoice cannot override toString() in Object (same thing at line 49)

和

line 59 cannot find symbol . myCustomer.setTrn(112233778)

line 60 cannot find symbol . myCustomer.setPersentage(150)

我的程序如下:

      class Invoice
      {


      int trn; //TAX REGISTRATION NUMBER
      int persentage;
      public Invoice{}

      public int setTrn(int trn){
        this.trn = trn;
      } 

      public int getTrn(){
         return trn;
      }

      public void setPersentage(int persentage){
          this.persentage = persentage;
      } 

      public int getPersentage(){
          return persentage;
      }

      String toString(){
          System.out.println(trn+" : "+persentage);
      }
 }   

 class Customer{

    int trn;
    int charging= 0;

    public Customer(int trn){
        this.trn = trn;
    }

    public int charge(int amount){
        charging = charging + amount;
    } 

    public int charge(int amount , int trn){
        if (this.trn == trn){
            charging = charging + amount;
        }
    }

    String toString(){
        System.out.println(trn+" : "+charging);
    }
}

 class TestCustomer
{
    public static void main(String[] args){
        Customer myCustomer = new Customer(112233778);
        myCustomer.charge(100);
        myCustomer.setTrn(112233778);
        myCustomer.setPersentage(150);

        System.out.println(myCustomer);
    }
}

Answer 1

几件事，

1. 您需要将 toString 方法声明为 public
2. 您需要在 toString 方法中返回一个字符串
3. 我强烈建议您添加 @Override重写方法时的表示法以确保您确实重写了该方法
4. 发生找不到符号...是因为这些方法未在Customer中定义，您在Invoice中定义了这些方法