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

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.

プロパティ

クラス名

Useless Assignment to Default (Java)

日本語クラス名

Useless Assignment to Default (Java)

クラス分類

信頼性 (reliability)

ニーモニック

JAVA.STRUCT.UA.DEFAULT

カテゴリー

CWE	CWE:665	Improper Initialization

対応言語

Java で利用可能です。

有効/無効設定

このワーニングクラスのチェックはデフォルトで有効になっています。チェックを無効にするにはプロジェクト設定ファイル（configuration file）に以下の WARNING_FILTER ルールを追加してください。

WARNING_FILTER += discard class="Useless Assignment to Default (Java)"

例

// 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);
  }

  //...
}

解決法

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

関連のある設定ファイルパラメータ

設定ファイルの以下のパラメータがこのワーニングクラスのチェックに影響します。