Java

JAVA.STRUCT.UA.DEFAULT : Useless Assignment to Default (Java)

Summary

A field is assigned to its default value inside a constructor or finaliser.

This checker finds assignments to local variables that are useless and could be consequently removed from code, hence obtaining a more efficient program. In some cases, these assignments hide actual bugs in the logic of the code.

Properties

Class Name Useless Assignment to Default (Java)
Significance reliability
Mnemonic JAVA.STRUCT.UA.DEFAULT
Categories
CWE CWE:665 Improper Initialization
Availability Available for Java only.
Enabling Checks for this warning class are enabled by default. To disable them, add the following WARNING_FILTER rule to the project configuration file. 
WARNING_FILTER += discard class="Useless Assignment to Default (Java)"

Example 

// Test.java
import java.util.HashMap;
import java.util.Map;

public class Test {
  private int f;
        
  public Test(int f) {
      f = process(f);                                 /* Unused Value: Write to Parameter (Java) 
                                                       *  warning issued here: programmer probably intended to write into 
                                                       *  this.f, which instead remains uninitialized. 
                                                       */   
      Map<String, Integer> factory = new HashMap<>(); // Unused Value: Variable (Java) warning issued here. 
      factory = buildFactory();
      go(factory);
  }

  private int process(int x) {
      return x * 17 + 13;
  }

  private Map<String, Integer> buildFactory() {
      Map<String, Integer> result = new HashMap<>();
      result.put("value", f);
        
      return result;
  }

  private void go(Map<String, Integer> factory) {
      for (String s: factory.keySet())
          System.out.println(s);
  }
  
  boolean b = false;                                  // Useless Assignment to Default (Java) warning issued here. 
 
  private foo(){
      int n = 0;
      // ...
      n = n;                                          // Useless Assignment (Java) warning issued here. 
      // ...
  }
}

In this example, the programmer should probably write into field f and initialize factory to the return value of buildFactory(), immediately, as follows.

// Test.java, after modification 
import java.util.HashMap;
import java.util.Map;

public class Test {
  private int f;
        
  public Test(int f) {
      this.f = process(f);
      Map<String, Integer> factory = buildFactory();
      go(factory);
  }

  //...
}

Resolution

Remove the assignment and check if it actually hid a more serious algorithmic issue.

Relevant Configuration File Parameters

The following configuration file parameters affect checks for this warning class.