Use reflection to dynamically invoke methods

This sample code uses class reflection associated with an ActionListener to dynamically invoke the specified method at runtime. The method name and parameters can be set differently under different conditions and for different source objects.

In the code, class MethodRelection has three JTextField fields and an objModified method. When any of the JTextField fields is modified, the objModified method will be called to handle the modification accordingly.

import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class MethodReflection extends JFrame{
    public MethodReflection() {
        JTextField[] data = {new JTextField("Peach", 20),
                                  new JTextField("Papaya", 20),
                                  new JTextField("Mango", 20)};
        JPanel panel = new JPanel(new GridLayout(3, 1));
     
        for (int i=0; i<data.length; i++){
            try {
                data[i].addActionListener(new ObjectActionListener(this,
                                                   "objModified",
                                                   new Object[]{data[i], "Field "+(i+1)+" Modified"}
                ));
                panel.add(data[i]);
            } catch (NoSuchMethodException e){
                System.out.println(e.getMessage());
            }
        }
     
        this.add(panel);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setSize(700, 300);
        this.pack();
    }
 
    public static void main(String[] args){
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                (new MethodReflection()).setVisible(true);
            }
        });
     
     
    }
 
    public class ObjectActionListener implements ActionListener {
        private Object methodSource = null;
        private Object[] parameters = null;
        private String methodName = null;
        private Method method = null;

        public ObjectActionListener(Object methodSource, String methodName, Object[] parameters)
                throws NoSuchMethodException, SecurityException {
            this.methodSource = methodSource;
            this.methodName = methodName;
            if (parameters == null) {
                parameters = new Object[0];
            }
            this.parameters = parameters;
            method = getMethod();
        }

        private Method getMethod() throws NoSuchMethodException {
            Class theClass = methodSource.getClass();

            Class[] paramTypes = new Class[parameters.length];
            for (int i = 0; i < parameters.length; i++) {
                paramTypes[i] = parameters[i].getClass();
            }
            return theClass.getMethod(methodName, paramTypes);
        }

        public void actionPerformed(ActionEvent event) {
            try {
                method.invoke(methodSource, parameters);
            } catch (IllegalAccessException e) {
                System.out.println(e.getMessage());
            } catch (InvocationTargetException e) {
                System.out.println(e.getMessage());
            } catch (Exception e) {
                System.out.println(e.getMessage());
            }
        }
    }
 
    public void objModified(JTextField obj, String message){
            String text = obj.getText();
            System.out.println(message+": "+text);
    }
}

The code using MethodHandle to dynamically invoke method can be found here

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