了解==和等于

Question

I learned that == checks if the references being compared are the same,, while .equals() compares the two states. So then why can we use == inside the .equals() method?

Like for example:

public boolean equals(Object o){
        //cast o to SimpleBankAccount
        SimpleBankAccount b = (SimpleBankAccount)o;

        //check if all attributes are the same
        if ((this.balance == b.balance) && (this.accountNumber == b.accountNumber)){
            return true;
        }
        else{
            return false;
        }
    }

Why would the this.balance and b.balance have the same reference?

Answer 1

The equals method is to compare objects. When using the "==" to test for equality, the only time it will function as expected is when it is comparing primitive or native types, or you are actually testing to see if two pointers refer to the same object. That is, balance is more than likely of type int , float or double , which means "==" will test for equality as expected. If balance was of type Balance , then this would not work.

Answer 2

引用也与基本类型以及int，char和double相似，因为在执行==时，您实际上是在比较这些类型的二进制表示形式。

Answer 3

because balance is likely a primitive, correct? like an int or a float? so you are comparing the value of balance. With objects you are comparing the references, but with primitives you are comparing the actual data value

Answer 4

如果此equals方法有效，那是因为balance和accountNumber变量是原始类型，例如int或double ，并且==会比较原始类型的值。

Answer 5

Depends on what balance is.

If balance is a primitive, then == will compare the values, which is correct.

Answer 6

== is normally used inside the equals method to check if the two references are actually the same object. If they are not, further checking goes to see if objects have the same state.

Answer 7

If you want to compare the value of balance/accountNumber and they are primitives or primitive Wrappers (like Integer) then == is how you compare the value. The wrappers will be autoboxed.