How to automatically remove methods in java code

Question

I need to remove some methods in a large java project and I was wondering if there are tools that would help me do so. I would basically specify a signature and a source folder in which all the matching method would be removed.

It no such thing exists then I will write a script.

Answer 1

I looked for quick solutions and did not find any, I used different tools to get there:

1. grep to find all the files containing the main methods I wanted to remove
2. find/replace in these files to make those methods private
3. Eclipse clean-up with just one rule: remove unused private methods

It did the job with the minor side effect of removing other unused private methods. It is not a big deal in the context of that project since pretty much all the files were previously saved with a save action removing unused private methods.

Thanks all for the input, it may be applicable later on.

Answer 2

If you use eclipse or other powerful IDE you may have built in support for doing this. See I can't delete a method using eclipse refactoring? for a way to achieve what you want.

Answer 3

Today, there are a couple of way to achieve this. For example, you can tell the Eclipse compiler to give you the AST (see my blog for an example). You can navigate the AST to find methods and remove nodes to change the source.

This makes it easy to keep the code valid. Using the Eclipse code formatter, you can clean up the formatting afterwards.

Projects like MoDisCo go one step further by analyzing a whole project and giving you ways to search the whole thing. I just found that the documentation for MoDisCo is not very helpful when you're a beginner.

Answer 4

You're talking about a "source transformation", and Google turns up the existence of BeautyJ for Java:

http://beautyj.berlios.de/

"BeautyJ can convert Java source code to XML and back. BeautyJ introduces the XJava format which stores classes or interfaces and their members together with associated source code and Javadoc comments in a single XML file. BeautyJ opens up a wide range of possibilities for automatic structuring of Java source code either by its Sourclet API or by converting Java source code to XML and allowing any external transformations (for example by applying XSLT)."

No clue whether your case is so simple that a script would be better than going through the trouble of learning how to use such a program, though. Although it may be worthwhile to get it in your toolchain for other purposes as well.

Answer 5

Our DMS Software Reengineering Toolkit with its Java Front End could be used for this.

DMS parses languages (using its front ends, in this case Java), builds ASTs and symbol tables, and provide facilities to manipulate the ASTs based on custom analysis. In this case OP wants to provide a method signature (presumably with a context in which it should be interpreted because otherwise the types used in the signature might not be defined), look that signature up in the symbol table, find the point of declaration (this is in the symbol table) as a AST node, and then apply a rewriting rule that replaces the declaration with an empty declaration.

An analysis he may wish to perform on the found method is whether is it used or not. We have that information in the symbol table, too.

Answer 6

You can use something in Java to batch-modify your Java project. The trick is to use a custom annotation processor. With annotation processor you can modify almost everything.

For an example, this library ( for ecilipse and IDEA ) modifies some String field members to it's /**multiline*/ docs.

Studying the library gives me the power to modify the method body as well.

Today, I want to strip out some unwanted methods in the android support library( used as editable local module ). I can manually remove them, but it would be hard to keep udpate after that.

So, instead of using script or mere-hand to modify the code directly, I decide to write another annotation processor which allow you to remove some class members.

For IDEA, the concept-proving code is very simple:

// the custom annotation 
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.SOURCE)
public @interface StripMethods {
    boolean strip() default true;
    String key() default "";
}

// processing the custom annotation 

@Override
public boolean process(final Set<? extends TypeElement> annotations, final RoundEnvironment roundEnv) {
    Set<? extends Element> fields = roundEnv.getElementsAnnotatedWith(StripMethods.class);
    for (Element field : fields) {
        StripMethods annotation = field.getAnnotation(StripMethods.class);
        ElementKind KIND = field.getKind();
        if(KIND == ElementKind.CLASS) {
            // the class declaration
            JCTree.JCClassDecl laDcl = (JCTree.JCClassDecl) elementUtils.getTree(field);
            // the definition tree list
            ArrayList<JCTree> defs = new ArrayList<>(laDcl.defs);
            // remove the second member which in this case is a string field 
            defs.remove(2);
            // finally modify the class definition
            laDcl.defs = List.from(defs);
        }
    }
}

@StripMethods
public class Test {
    // the first member is the default constructor
    static {
    }
    
    static final int FieldToRemove = 0;
        
    @Test
    public void test() {
        int variableToRemove = FieldToRemove; 
    }
}

the result error caused by the member removal:

Test.java:10: error: cannot find symbol
        int variableToRemove = FieldToRemove;
                               ^
  symbol:   variable FieldToRemove
  location: class Test

Still a long way to go. I will publish the code when it's finished.

---

Done. see https://github.com/KnIfER/Metaline

Exmaple usage, removing NightMode from androidx/appcompat:

  @StripMethods(key="Night")
  public class AppCompatActivity
  ...
  @StripMethods(key="Night")
  public abstract class AppCompatDelegate
  ...
  @StripMethods(key="Night")
  class AppCompatDelegateImpl 
  ...