Why are two objects with same data not equal while using equals() method [duplicate]

Question

public class Account {

    String account;
    double balance;

    Account(String account, double balance) {
        this.account = account;
        this.balance = balance;
    }
}

public class AccountTest {

    public static void main(String[] args) {
        Account a1 = new Account("Sandy", 1000);
        Account a2 = new Account("Sandy", 1000);
        System.out.println(a1.equals(a2));
    }
}

When i execute it showing "false" but objects contains same data in variables.why?explain.

Answer 1

Because by default object checks equality based on equals(Object obj).

The equals method for class Object implements the most discriminating possible equivalence relation on objects; that is, for any non-null reference values x and y, this method returns true if and only if x and y refer to the same object (x == y has the value true).

If you want to check equality with equals() method in your class equal you have to override equals() method of Object class.
how-to-override-equals-method-in-java, Like following:

@Override
public boolean equals(Object obj) {
   // your implementation 
}

And you should always override hashCode() whenever overriding equals method of Object class.

#Effective Java, by Joshua Bloch

You must override hashCode() in every class that overrides equals(). Failure to do so will result in a violation of the general contract for Object.hashCode(), which will prevent your class from functioning properly in conjunction with all hash-based collections, including HashMap, HashSet, and Hashtable.

Answer 2

You need to override equals() method, and use it whenever you want to compare their values.

@Override
public boolean equals(Object obj) {
    if (obj == null) {
        return false;
    }
    if (getClass() != obj.getClass()) {
        return false;
    }
    final Account other = (Account) obj;
    if ((this.account== null) ? (other.account!= null) : !this.account.equals(other.account)) {
        return false;
    }
    if (this.balance!= other.balance) {
        return false;
    }
    return true;
}

BUT WHY I HAVE TO OVVERIDE EQUALS()