SCP00-J. Use as minimal scope as possible for all variables and methods

Scope minimization helps to capture common programming errors, improves code readability by tying together the declaration and actual use and eases maintainability since unused variables are easily caught and removed.

Noncompliant Code Example

This noncompliant example shows a variable that is declared outside the for loop. This can harm reusability since the loop index i will change after the for statement. Consider for instance, if this code snippet is copy pasted with the intent of using a different index j but the statement mistakenly still iterates over index i. Since i is still in scope, this will lead to a rather obtuse outcome.

public class Scope {
  public static void main(String[] args) {
    int i=0;
    for(i=0;i<10;i++) {
    	//do operations
    }
  }
}

Compliant Solution

To be compliant, minimize scope where possible, such as by declaring loop indexes within the for statement.

public class Scope {
  public static void main(String[] args) {
    for(int i=0;i<10;i++) { //contains declaration
    	//do operations
    }
  }
}

Additionally, methods should be designed for only one operation if possible. This simplicity avoids variables from existing in overlapping scopes.

Risk Assessment

Using a larger scope than necessary results in less reliable code.

Automated Detection

TODO

Related Vulnerabilities

Search for vulnerabilities resulting from the violation of this rule on the CERT website.

References

[[JLS 05]] Section 14.4.2, Scope of Local Variable Declarations
[[Bloch 01]] Item 29, Minimize the scope of local variables

03. Scope (SCP)      03. Scope (SCP)      SCP01-J. When developing Java clients (applets, mobile) assume that all scope can be overridden or modified