CODEWITHSUNDEEP
javaandroid
user1072357
user1072357

Reputation:

Is super doing anything if so Can someone explain

I am looking through the net and finding examples of code and trying to understand them. in this one I believe super is doing nothing is that correct. in eclipe it tells me it comes from Objects class. in Java there is a tutorial.

I am trying to learn the connections between Me creating Objects into a "ArrayAdapter" into a "ListAdapter" and in the Android 4 opening template they use "ListFragment" so i would be made to belive even though i don't understand this it is corrent to learn this way of adding lists to a page for "Master Detail" selection.

links Java tutorial :: Android doc :: ArrayAdapter tutorial

I guess I just missed the boat.

public class Weather {
public int icon;
public String title;

public Weather(){
    super();
}

public Weather(int icon, String title) {
    super();
    this.icon = icon;
    this.title = title;
}
}

Upvotes: 0

Views: 77

Answers (2)

Evgeniy Dorofeev
Evgeniy Dorofeev

Reputation: 136132

It is not correct to say that super() is doing nothing. It calls its super class's no-arg constructor. Even if the class inherits directly from java.lang.Object then Object's constructor is called, though it does nothing. Of course JVM optimizer will quickly eliminate such useless calls.

Upvotes: 0

JB Nizet
JB Nizet

Reputation: 692181

Invoking super() in a constructor is never necessary, because if you don't, the compiler inserts this instruction for you.

So 

public Foo() {
    // some instructions
}

and 

public Foo() {
    super();
    // some instructions
}

are strictly equivalent. The first thing a constructor must do is to invoke one of the superclass constructors. If you forget to do it, the compiler does it for you by inserting a super() call. And if the superclass doesn't have a visible no-arg constructor, you'll get a compilation error.

Invoking super(someArguments) is often necessary when you want (or need) to invoke a constructor of the base class that is not the no-arg constructor.

Upvotes: 5

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