How to get class level variable names using javaparser?

Question

I was able to get class level variable's declarations using the following code. But I only need the variable name. This is the output I get for following code - [private boolean flag = true;]

import com.github.javaparser.JavaParser;
import com.github.javaparser.ast.CompilationUnit;
import com.github.javaparser.ast.body.ClassOrInterfaceDeclaration;
import com.github.javaparser.ast.visitor.VoidVisitorAdapter;
import java.io.FileInputStream;

public class CuPrinter{
    public static void main(String[] args) throws Exception {
        // creates an input stream for the file to be parsed
        FileInputStream in = new FileInputStream("C:\\Users\\arosh\\IdeaProjects\\Bot_Twitter\\src\\MyBot.java");

        CompilationUnit cu;
        try {
            // parse the file
            cu = JavaParser.parse(in);
        } finally {
            in.close();
        }
        cu.accept(new ClassVisitor(), null);
}
private static class ClassVisitor extends VoidVisitorAdapter<Void> {
    @Override
    public void visit(ClassOrInterfaceDeclaration n, Void arg) {
        /* here you can access the attributes of the method.
         this method will be called for all methods in this
         CompilationUnit, including inner class methods */
        System.out.println(n.getFields());
        super.visit(n, arg);
    }
  }
}

You can probably iterate over `n.getFields()` and retrieve the name — Lino, Jun 04 '18 at 12:26
No. I want to parse many java files and find their class level variables. So I don't know whats will be the variable name, modifier, type while iterating. I want a general way to get class level variables. — Arosha Mudalige, Jun 04 '18 at 12:30
As said, `n.getFields()` will return an array of custom objects or even a whole new object. Which then can be generically iterated over — Lino, Jun 04 '18 at 12:32
n.getFields() can be like [private boolean flag = true;] or [private boolean flag;] or [boolean flag = true;]. So in that case while coding how can I know which element of the array will be the variable name. For example in 1st one it is the 3rd element and in 2nd one it is the 2nd element. — Arosha Mudalige, Jun 04 '18 at 12:38
If I have two class level variables. I get this - [public int total;, private int sum;] — Arosha Mudalige, Jun 04 '18 at 12:52
I guess you could solve that with regex. I have to try that out, give me some time ;) — Lino, Jun 04 '18 at 12:57

score 4 · Accepted Answer · answered Jun 04 '18 at 13:05

You can use the following simple regex:

final String regex = "^((private|public|protected)?\\s+)?.*\\s+(\\w+);$";

Which then can be compiled into a Pattern:

final Pattern pattern = Pattern.compile(regex);

And then finally be used in a for-loop:

for(final String field : n.getFields()){
    // create a regex-matcher
    final Matcher matcher = pattern.matcher(field);

    // if field matches regex
    if(matcher.matches()){
        // get the last group -> the fieldName
        final String name = matcher.group(matcher.groupCount());
        System.out.println("FieldName: " + name);
    }
}

@AroshaMudalige You're welcome. Be aware that this only works for single fields declared like: `private MyClass someName;`. But not for multiple field declaration like: `private int x,y;`. Also `final` is not taken into account — Lino, Jun 04 '18 at 13:21

score 2 · Answer 2 · answered Jun 05 '18 at 10:16

You can try this. If you have more than one variables in FieldDeclarations, use one more for loop inside.

public void visit(ClassOrInterfaceDeclaration n, Void arg) {

    super.visit(n, arg);
    for(FieldDeclaration ff:n.getFields())
    {
        System.out.println(ff.getVariable(0).getName());
    }
}

How to get class level variable names using javaparser?

2 Answers2