Program to demonstrate how to determine information about class methods at runtime using Java Reflection API.
package com.hubberspot.reflection;
import java.lang.reflect.Method;
// Create a dummy class having methods which are
// private, protected and public. It should have
// a return type and few parameters.
class Cricket {
private int runs;
private String playerName;
public void setRun(int runs) {
}
protected int getRun(int rate) {
return rate*runs;
}
private void playerName( String name ) {
playerName = name;
}
public void playerRuns(int rate , int runs , String playerName) {
}
}
public class MethodFindings {
public static void main(String[] args) {
// Creating a instance of class Class of type Cricket
Class cricketClass = Cricket.class;
// object of class Instance has a method by name
// getMethods() which returns back a list of
// public methods in the form of array
// The array type is of Method class
Method[] methodsArr = cricketClass.getMethods();
for (int j = 0; j < methodsArr.length; j++) {
// Method class has method by name getName()
// which returns back the name of the method
String methodName = methodsArr[j].getName();
System.out.println("Name of the method : " + methodName);
// Method class also has a method by name getReturnTypes()
// which returns a Class object that represents the formal
// return type of the method represented by Method object.
String returnType =
methodsArr[j].getReturnType().getName();
System.out.println("Return Type of the method : " + returnType);
// Method class also has a method called as getParameterTypes().
// Returns an array of Class objects of parameter types,
// in declaration order. Returns an array of length 0 if
// the underlying method takes no parameters.
Class[] parameterTypes =
methodsArr[j].getParameterTypes();
System.out.print("Parameter Types in the method :");
for (int k = 0; k < parameterTypes.length; k ++) {
String paramTypeName = parameterTypes[k].getName();
System.out.print(" " + paramTypeName);
}
System.out.println();
}
System.out.println("-------------------------------------------");
System.out.println("For methods that are declared private and protected etc... ");
// Class object also has a method by name getDeclaredMethods().
// Returns an array of Method objects reflecting all the methods
// declared by the class. This includes public, protected,
// default access and private methods, but excludes inherited methods.
// Rest of the code is same as above .....
methodsArr = cricketClass.getDeclaredMethods();
for (int j = 0; j < methodsArr.length; j++) {
String methodName = methodsArr[j].getName();
System.out.println("Name of the method : " + methodName);
String returnType =
methodsArr[j].getReturnType().getName();
System.out.println("Return Type of the method : " + returnType);
Class[] parameterTypes =
methodsArr[j].getParameterTypes();
System.out.print("Parameter Types in the method :");
for (int k = 0; k < parameterTypes.length; k ++) {
String paramTypeName = parameterTypes[k].getName();
System.out.print(" " + paramTypeName);
}
System.out.println();
}
}
}
Output of the program :