不兼容的返回类型错误java

Question

class BankAccount {
    private String firstname;
    private String lastname;
    private int ssn;
    private int accountnumber = 0;
    private double accountbalance = 0.0;

    BankAccount() {
        firstname = "John Smith";
    }

    BankAccount(String firstname, String lastname, int ssn) {
        int accountnumber;
        double accountbalance;
    }

    public String getName() {
        return firstname;
    }

    public double getBalance() {
        return accountbalance;
    }

    public void setAccountNumber(int accountnumber) {
        return accountnumber;
    }

    public boolean equals(BankAccount ba) {
        return this.accountbalance == ba.accountbalance;
    }

    public void deposit(double amount) {
        return this.accountbalance = this.accountbalance + amount;
    }

    public int withdraw(double amount) {
        this.accountbalance = this.accountbalance - amount;
        if(accountbalance < 0) {
            this.accountbalance = this.accountbalance + amount;
            return -1;
        }
        else
           return 0;
    }

    public String toString() {
        return firstname+lastname+"/n"+"social secuirty "+"ssn"+"/n"+"account number is "+
        "accountnumber" +"/n" +"Balance:" +"accountbalance" +"/n";
    }
}

错误是:

BankAccount.java:34: error: incompatible types: unexpected return value
return accountnumber;
       ^
BankAccount.java:47: error: incompatible types: unexpected return value
return this.accountbalance=this.accountbalance+amount;
                          ^
2 errors

我做错了什么？

Answer 1

一种void方法不能return有所作为.并且具有返回类型的方法必须return是方法签名中指定的类型.

错误1

例如,看看这个方法

 public void setAccountNumber(int accountnumber) {
   return accountnumber;
   }

哟不能从一个void方法返回.

那应该是

  public void setAccountNumber(int accountnumber) {
           this.accountnumber =accountnumber;
       }

其余方法也是如此.

错误2

public void deposit(double amount) {
        return this.accountbalance = this.accountbalance + amount;
    }

返回语句在语法上是错误的.你无法返回,因为它是无效的.那应该是

  public void deposit(double amount) {
            this.accountbalance = this.accountbalance + amount;
        }