JAVA.STRUCT.UA : Useless Assignment (Java)

JavaScript is not currently enabled, but is required for full CodeSonar manual search and browse functionality.

If you are viewing this file in your hub's Web GUI, enable JavaScript in your browser: you will also need it for GUI functionality.

If you opened this file directly from disk, your browser may be directly suppressing JavaScript functionality: certain browsers perform this suppression on local files (but not files delivered by web servers) for security reasons.

If you access the manual through the hub's Web GUI, the functionality will not be suppressed because the hub is a web server.
Alternatively, your browser may allow you to explicitly disable the security setting that suppresses functionality. See the CodeSonar FAQ for more information.

CodeSonar^® 9.2p0

CONFIDENTIAL

CodeSecure Inc

JAVA.STRUCT.UA : Useless Assignment (Java)

Summary

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

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.