CODEWITHSUNDEEP
javascopenaming-conventions
LuckyLuke
LuckyLuke

Reputation: 49097

How to avoid that local declarations hide higher level declarations

I am reading the Java Code Conventions PDF and I noticed this:

Avoid local declarations that hide declarations at higher levels. For example, do not declare the same variable name in an inner block:

int count;
         ...
         func() {
             if (condition) {
                 int count;
... }
... }

It is nothing new and I frequently find myself writing such code. How do you solve such cases? Of course you can say "find a better name", but that is not always easy. Are there any conventions on adding something in front or back of the higher level name?

Upvotes: 1

Views: 237

Answers (5)

Makoto
Makoto

Reputation: 106498

You can use scope-specific variable naming conventions to reduce confusion.

String[] names;

public void populateNames(String[] theNames) {
    names = theNames;
}

Also, you can explicitly state which scoped variable you want by use of the this keyword.

int count = 0;
public void func() {
    int count = 0;
    if (condition) {
        this.count++; // increment the class-scope count variable
    } else {
        count++; // increment the local scope variable
    }
}

In general, just don't reuse your variable names. It confuses those that read your code, and makes debugging a bit harder.

Upvotes: 2

assylias
assylias

Reputation: 328855

I have seen this coding style used in a library:

  • member variables: _variable
  • local variable: locVariable
  • methods arguments (parameters): parVariable

But I personally think it clutters the code.

Any good IDE will use a colour code that makes a clear difference between a local variable and a class member.

Upvotes: 0

Edd
Edd

Reputation: 3822

If you're only dealing with method variable declarations, you can use the this keyword to refer to the instance variable as in the following example:

public class Foo {
    private int id;

    public void setId(int id) {
        this.id = id;
    }
}

Here, this.id refers to the instance variable, whereas id refers to the parameter passed in to the setter.

I know you said that you don't want to hear suggestions of using better variable names, but I do think the only situation you should really have duplicated names are when you're preparing to set a new value for an ivar, or have just read an ivar. Even then, it's often more readable to use names with a bit more meaning, so for example if you only need a variable that is of the same time as barr temporarily, name it tmpBarr or something similar.

Upvotes: 0

Dmitry Zaytsev
Dmitry Zaytsev

Reputation: 23972

Top level variables have more "detailed" names that lower ones. For example:

class A{

    private int mVegetablesCount;

    public void foo(){
        int count;
        if(true){
           int cnt;
             if(true)
                int c;
        }
    }
}

Just as variant. Also, it's good idea to name your class fields specificaly. In my example field named fith prefix "m".

Upvotes: 0

Martin.
Martin.

Reputation: 10539

int count;
count = 1;

is not the same as 

int count;
this.count = 1;

So if you work with local variable, you just don't user "this."

Upvotes: 0

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