How does Java handle using a getter on a for loop?

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For instance, if I have the below for loop declaration.

for(Foo f : fooService.getFooList()){}

Is it more efficient to call the getter first and assign it to a temporary List<Foo> fooList = fooService.getFooList(); or is it ok to use the getter inline?

In this specific case, with a foreach loop, I expect your code will compile to something like this:

Iterator<Foo> it = fooService.getFooList().iterator();
while (it.hasNext()) {
    Foo foo = it.next();
    // ...
}

So in this case it doesn't make a difference.

However if you were to use a different kind of loop, then it might make a difference. For example:

for(int i = 0; i < fooService.getFooList().size(); i++){
    Foo foo = fooService.getFooList().get(i);
    // ...
}

If your list is exposed to external modification, then it's unlikely that the compiler could prove that the list size wont change, so it will call getFooList().size() each iteration to compare against i, so there would be some slight added overhead.

But note that if the list size changes then i < fooService.getFooList().size() reflects that. This can be useful if you are aware of it but dangerous if you aren't.

If you know that the list size wont change then you could do something like this to eliminate that overhead (or just use an Iterator or enhanced for-each loop if you don't need the indices):

List<Foo> fooList = fooService.getFooList();
final int fooListSize = fooList.size();
for(int i = 0; i < fooListSize ; i++){
    Foo foo = fooList.get(i);
    // ...
}

Despite all this, you should probably prefer readability over micro optimization.

But if your application is runtime sensitive and your list is large and these small checks are adding up, then you may want to do something like the above.

In this post, we take a closer look at getter and setter methods in Java, common mistakes, By using getter and setter, the programmer can control how their important variables are Setters, Method Handles, and Java 11  Introduction to Java Getter Setter. Getters and Setters in java are two methods used for fetching and updating the value of a variable. Getter methods are concerned with fetching the updated value of a variable while a setter method is used to set or update the value of an existing variable.

It's not more efficient to assign to a List reference first, but having the reference may be useful, depending upon what you're trying to do.

The get method returns the variable value, and the set method sets the value. Syntax for both is that they start with either get or set , followed by the name of the​  The meaning of Encapsulation, is to make sure that "sensitive" data is hidden from users. To achieve this, you must: provide public get and set methods to access and update the value of a private variable. You learned from the previous chapter that private variables can only be accessed within the same class (an outside class has no access to it).

If your concern is about the fooService.getFooList() being called n times for getting every value f disregard that thought. This calls getFooList() once and iterates over its result.

For example in the following snippet:

class Ideone
{
    private static List<String> list = Arrays.asList("A", "B", "C");

    public static void main (String[] args) throws java.lang.Exception
    {
        for(String f : getFooList()){
           System.out.println(f);
        }
    }

    private static List<String> getFooList() {
        System.out.println("getFooList called");
        return list;
    }
}

getFooList called is printed only once which indicates that the method getFooList() is invoked only once by the for-loop. After that it is printed A, B, C, the iteration over the elements gotten from the method invokation.

So, in terms of efficiency, it is the same calling the getter directly or assigning it to a variable and using this for performing the iteration.

For a better understanding, developers can execute the below code in Eclipse Ide. 2.1 Example with Setter & Getter. In this example, we will  Once we've defined a method handle, it's possible to enhance it by binding the method handle to an argument without actually invoking it. For example, in Java 9, this kind of behaviour is used to optimize String concatenation. Let's see how we can perform a concatenation, binding a suffix to our concatMH:

It is exactly the same. The getter is called once, not before completing each loop. Assign it to a variable if you need it, otherwise it is not necessary.

FYI : behind the scene the List won't be used itself but its Iterator.

Your for loop can thus be formulated that way:

for (Iterator<Foo> i = fooService.getFooList(); i.hasNext();) {
    Foo foo= i.next();
}

See the language specifications about the for loops for more information

The attributes contained in the “secondary” (non-main) concepts are handled by the Both loops are similar and differ only in the direction ('target' vs. the appropriate names for the property and its getter and setter operations. Then these elements are added to the DTO class using appropriate object creation constructs. Java provides two different options to handle an exception. You can either use the try-catch-finally approach to handle all kinds of exceptions. Or you can use the try-with-resource approach which allows an easier cleanup process for resources. Try-Catch-Finally. That is the classical approach to handle an exception in Java. It can consist of 3

Column names as input to the getter methods are not case sensitive. We loop through the rows contained within the ResultSet using the next() method Input parameters are handled exactly as they are when using a Prepared Statement. Statement 1 sets a variable before the loop starts (int i = 0). Statement 2 defines the condition for the loop to run (i must be less than 5). If the condition is true, the loop will start over again, if it is false, the loop will end. Statement 3 increases a value (i++) each time the code block in the loop has been executed.

The following example shows the Statement object and executeQuery method Host languages such as Java are essentially record-oriented: they cannot handle For every row, fields can be retrieved using the get____-collection of “getter”  Usually, Java libraries that use reflection on getters and setters are doing it to bind data to/from these objects. There is usually a specific intent behind this, such as to create a POJO from incoming data, such as from the JSON body of an http request.

Let's make getters and setters our last, rather than first, resort. The point here is that anything I can do with Car2.java, I can do with Car1.java, and vice-versa. I need to be able to see a person's debts to give them a statement. For example the way Hibernate handles DB properties, or ActiveRecord. Here we're using both getters and setters. First, we use a getter to get and display the cat's original name. Then, we use a setter to assign a new name ("Mr. Smudge"). And then we use the getter once again to get the name (to check if it really changed). Console output: Cat's original name: Smudge Cat's new name: Mr. Smudge So what's the

Comments
  • The only difference between these two is style. They are functionally identical.