I am trying to figure out what the toString method does. I have looked a lot on youtube and googled a lot. But it's something that I am missing out. Please note that I have done java about 80 hours in total.
I do know that toString is a name on a method (?) that has a built in function. When should I use this? When i mix up string and int/doubles?
And second question that might be answered with the first one. How does it work when I use this toString? Same as usually? No changes?
toString() returns a string representation of the object that it is called on.
When you call toString() on an object, it may give you a String that does not make much sense. When you pass an object into System.out.println(), this function calls the object's toString() method.
You call override the toString() of your class so a human readable string will be provided when toString() is called on objects of your class.
toString() is very useful for logging, debugging, or any time you want to render/display an object as a String.
toString is a method in Object class which is parent of all the classes. When you define your own custom class, and if you want to log it in nice readable way, so you get to know state of your customized object, then you define toString method by overriding one present in Object class. Consider following employee class like:
public class Employee {
private int id;
private String name;
..
@Override
public String toString() {
return "id: " + id +" name: " + name;
}
}
Now when say you try to write onto Standard output employee object, you will see like:
Employee employee = ...
...
System.out.println(employee);
Output:
id: .. name: ...
If you dont override it, then Object's toString would be called and it would be in unreadable form like:
Employee@abbcc..
tosTring is a method for converting your class to string. For example:
public class Person
{
private String name;
private String age;
private String address;
@Override
public String toString()
{
return String.format("%10s %2d %20s",name,age,address);
}
}
toString is a method on every Object which converts the logical binary representation in memory to a string of characters (String) in a human readable form.
The default behaviour of toString as seen in Object.java is to return:
class name + @ + memory address in hexadecimal
When you create your own classes it's worth to @Override this method to be able to easily find bugs later on. See SMA's answer on how to do this. Most of the framework's classes have this method already, for example ArrayList prints: [object 0's toString(), object 1's toString(), object 2's toString()].
When you add an arbitrary object to a String object, like "hello " + empoyee, toString is called in the background so it roughly becomes "hello " + employee.toString() (I say "roughly" because there's more magic involving StringBuilder, but that's not to be concerned about as a beginner).
It is mostly used for debugging and logging. It's considered bad practice to actually use it in production code and rely on the output of the method in business logic and UI.
