How can I list all methods of all imported classes in a file using Java?

Question

My objective is to look at some lines of codes of an external file and count the number of functions of a class are called then.

For example, if I have the following code:

import java.io.BufferedReader;
import whatever.MyClass;
import java.util.ArrayList;
...
...
public void example(){
    InputStreamReader isr = new InputStreamReader (whatever);
    MyClass object = new MyClass();
    someArrayList.add(whatever2)
    someArrayList.add(whatever3)
}

In this case, BufferedReader and MyClass functions were called once, and ArrayList functions were called twice.

My solution for that is get a list of all methods inside the used classes and try to match with some string of my code. For classes created in my project, I can do the following:

jar -tf jarPath

which returns me the list of classes inside a JAR . And doing:

javap -cp jarPath className

I can get a list of all methods inside a JAR whit a specific class name. However, what can I do to get a external methods names, like add(...) of an "external" class java.util.ArrayList? I can't access the .jar file of java.util.ArrayList correct? Anyone have another suggestion to reach the objective?

Answer 1

The compiler doesn't put the imports into the object file. It throws them away. Import is just a shorthand to the compiler.(Imports are a compile-time feature ).

first step :

use Qdox https://github.com/paul-hammant/qdox to get all the imports in a class :

String fileFullPath = "Your\\java\\ file \\full\\path";
JavaDocBuilder builder = new JavaDocBuilder();
builder.addSource(new FileReader( fileFullPath  ));

JavaSource src = builder.getSources()[0];
String[] imports = src.getImports();

for ( String imp : imports )
{
    System.out.println(imp);
}

second step : inspire from that code , loop through your imports (String array) and apply the same code and you will get the methods .

 import java.lang.reflect.Method;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;

  public class Tes {
  public static void main(String[] args) {
    Class c;
    try {
        c = Class.forName("java.util.ArrayList");
        Arrays.stream(getAccessibleMethods(c)).
                              forEach(System.out::println);
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    }
}

public static Method[] getAccessibleMethods(Class clazz) {
    List<Method> result = new ArrayList<Method>();
    while (clazz != null) {
        for (Method method : clazz.getDeclaredMethods()) {
            result.add(method);
        }
        clazz = clazz.getSuperclass();
    }
    return result.toArray(new Method[result.size()]);
}
}

Output :

  public void java.util.ArrayList.add(int,java.lang.Object)
  public boolean java.util.ArrayList.add(java.lang.Object)
  public boolean java.util.ArrayList.remove(java.lang.Object)
  public java.lang.Object java.util.ArrayList.remove(int)
  public java.lang.Object java.util.ArrayList.get(int)
  public java.lang.Object java.util.ArrayList.clone()
  public int java.util.ArrayList.indexOf(java.lang.Object)
  public void java.util.ArrayList.clear()
  .
  .
  .

All the code - one class :

  import java.io.FileNotFoundException;
  import java.io.FileReader;
  import java.lang.reflect.Method;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.List;

  import com.thoughtworks.qdox.JavaDocBuilder;
  import com.thoughtworks.qdox.model.JavaSource;

  public class Tester {
  public static void main(String[] args) {
  // put your .java file path
  // CyclicB is a class within another project in my pc
    String fileFullPath =
      "C:\\Users\\OUSSEMA\\Desktop\\dev\\OCP_Preparation\\src\\w\\CyclicB.java";
JavaDocBuilder builder = new JavaDocBuilder();
try {
    builder.addSource(new FileReader( fileFullPath  ));
} catch (FileNotFoundException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}

JavaSource src = builder.getSources()[0];
String[] imports = src.getImports();

for ( String imp : imports )
{
    Class c;
    try {
        c = Class.forName(imp);
        Arrays.stream(getAccessibleMethods(c)).
                              forEach(System.out::println);
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    }
 }
 }
  public static Method[] getAccessibleMethods(Class clazz) {
  List<Method> result = new ArrayList<Method>();
  while (clazz != null) {
    for (Method method : clazz.getDeclaredMethods()) {
        result.add(method);
    }
    clazz = clazz.getSuperclass();
  }
return result.toArray(new Method[result.size()]);
}
}

Output all the methods within the classes imported in the file CyclicB.java :

  private void java.lang.Throwable.printStackTrace(java.lang.Throwable$PrintStreamOrWriter)
  public void java.lang.Throwable.printStackTrace(java.io.PrintStream)
  public void java.lang.Throwable.printStackTrace()
  public void java.lang.Throwable.printStackTrace(java.io.PrintWriter)
  public synchronized java.lang.Throwable java.lang.Throwable.fillInStackTrace()
  .
  .
  .

Answer 2

You can get accessible methods using getAccessibleMethods() method you just need to pass the class as a parameter

getAccessibleMethods(Test)

It will return array of methods

public static Method[] getAccessibleMethods(Class clazz) {
        List<Method> result = new ArrayList<Method>();
        while (clazz != null) {
            for (Method method : clazz.getDeclaredMethods()) {
                int modifiers = method.getModifiers();
                if (Modifier.isPublic(modifiers) || Modifier.isProtected(modifiers)) {
                    result.add(method);
                }
            }
            clazz = clazz.getSuperclass();
        }
        return result.toArray(new Method[result.size()]);
    }