edu.pdx.cs.joy.reflect.DescribeClass Maven / Gradle / Ivy
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package edu.pdx.cs.joy.reflect;
import java.io.*;
import java.lang.reflect.*;
/**
* This program uses Java reflection to describe a class, its methods,
* and fields.
*/
public class DescribeClass {
private static PrintStream out = System.out;
private static PrintStream err = System.err;
/**
* Prints a description of a field
*/
private static void describe(Field f) {
out.print(" ");
out.print(Modifier.toString(f.getModifiers()));
out.print(" ");
out.print(f.getType().getName());
out.print(" ");
out.println(f.getName());
}
/**
* Prints a description of a method
*/
private static void describe(Method m) {
out.print(" ");
out.print(Modifier.toString(m.getModifiers()));
out.print(" ");
out.print(m.getReturnType().getName());
out.print(" ");
out.print(m.getName());
out.print("(");
Class[] params = m.getParameterTypes();
for (int i = 0; i < params.length; i++) {
out.print(params[i].getName());
if (i < params.length - 1)
out.print(", ");
}
out.println(")");
Class[] exs = m.getExceptionTypes();
if (exs.length > 0) {
out.print(" throws ");
for (int i = 0; i < exs.length; i++) {
out.print(exs[i].getName());
if (i < exs.length - 1)
out.print(", ");
}
out.println("");
}
}
/**
* Prints a description of a class
*/
private static void describe(Class c) {
out.print(Modifier.toString(c.getModifiers()));
out.print(" ");
out.print((c.isInterface() ? "interface " : "class "));
out.println(c.getName());
Class superclass = c.getSuperclass();
if (superclass != null) {
out.print(" extends ");
out.println(superclass.getName());
}
Class[] ifaces = c.getInterfaces();
if (ifaces.length > 0) {
out.print(" implements ");
for (int i = 0; i < ifaces.length; i++) {
out.print(ifaces[i].getName());
if (i < ifaces.length - 1)
out.print(", ");
}
out.println("");
}
out.println("{");
Field[] fields = c.getDeclaredFields();
for (int i = 0; i < fields.length; i++) {
describe(fields[i]);
}
out.println("");
Method[] methods = c.getDeclaredMethods();
for (int i = 0; i < methods.length; i++) {
describe(methods[i]);
}
out.println("}");
}
/**
* Main program that reads the name of a class from the command
* line, loads it, and prints out a description of it.
*/
public static void main(String[] args) {
String className = args[0];
try {
Class c = Class.forName(className);
describe(c);
} catch (ClassNotFoundException ex) {
err.println("Could not load " + className);
}
}
}