14 object class = = and equals

be-all java object （ Including arrays ） All of them Object Attributes of a class And methods
toString(); yes Object Attributes of a class And methods However, he is usually rewritten public String toString(){}
Method rewriting override
1 Usually, subclasses override parent methods Rewrite directly to overwrite （ name Same formal parameters ）
2. return type And declare exception types Subclass less than or equal to parent class The parent class returns the parent class of another class Subclasses can also Go back to this You can also return subclasses of this parent class But you cannot return a class larger than the parent class of this class

“==” Whether the representatives are the same If the basic type Then it means that the values are equal If it's a reference type said The address is equal The same object
equal yes Object A method is provided Define whether the object contents are equal Usually rewrite to judge
for instance In the public security system If the ID card is the same Auto same

Right click stand alone directly source add to equals Special comparison Let's judge by a certain item

if (this == obj) // If The addresses passed are equal Go straight back to true
return true;
if (obj == null)// If empty It's a mistake
return false;
if (getClass() != obj.getClass()) // If the types are different be false
return false;
User other = (User) obj; // Forced transformation Compare
if (id != other.id)
return false;
return true;
You can also write by yourself But pay attention to the return parameters
public boolean equals(User obj) {
if(this.id==obj.id) return true;

	return false;
}

Use default equals and == When judging an array Because arrays belong to objects So the return value must be false Because the comparison is the address