Mega Code Archive
A program that displays a class synopsis for the named class
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/*
* Copyright (c) 2004 David Flanagan. All rights reserved.
* This code is from the book Java Examples in a Nutshell, 3nd Edition.
* It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied.
* You may study, use, and modify it for any non-commercial purpose,
* including teaching and use in open-source projects.
* You may distribute it non-commercially as long as you retain this notice.
* For a commercial use license, or to purchase the book,
* please visit http://www.davidflanagan.com/javaexamples3.
*/
//package je3.reflect;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Member;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
/** A program that displays a class synopsis for the named class */
public class ShowClass {
/** The main method. Print info about the named class */
public static void main(String[] args) throws ClassNotFoundException {
Class c = Class.forName(args[0]);
print_class(c);
}
/**
* Display the modifiers, name, superclass and interfaces of a class or
* interface. Then go and list all constructors, fields, and methods.
*/
public static void print_class(Class c) {
// Print modifiers, type (class or interface), name and superclass.
if (c.isInterface()) {
// The modifiers will include the "interface" keyword here...
System.out.print(Modifier.toString(c.getModifiers()) + " " + typename(c));
} else if (c.getSuperclass() != null) {
System.out.print(Modifier.toString(c.getModifiers()) + " class " + typename(c) + " extends "
+ typename(c.getSuperclass()));
} else {
System.out.print(Modifier.toString(c.getModifiers()) + " class " + typename(c));
}
// Print interfaces or super-interfaces of the class or interface.
Class[] interfaces = c.getInterfaces();
if ((interfaces != null) && (interfaces.length > 0)) {
if (c.isInterface())
System.out.print(" extends ");
else
System.out.print(" implements ");
for (int i = 0; i < interfaces.length; i++) {
if (i > 0)
System.out.print(", ");
System.out.print(typename(interfaces[i]));
}
}
System.out.println(" {"); // Begin class member listing.
// Now look up and display the members of the class.
System.out.println(" // Constructors");
Constructor[] constructors = c.getDeclaredConstructors();
for (int i = 0; i < constructors.length; i++)
// Display constructors.
print_method_or_constructor(constructors[i]);
System.out.println(" // Fields");
Field[] fields = c.getDeclaredFields(); // Look up fields.
for (int i = 0; i < fields.length; i++)
// Display them.
print_field(fields[i]);
System.out.println(" // Methods");
Method[] methods = c.getDeclaredMethods(); // Look up methods.
for (int i = 0; i < methods.length; i++)
// Display them.
print_method_or_constructor(methods[i]);
System.out.println("}"); // End class member listing.
}
/** Return the name of an interface or primitive type, handling arrays. */
public static String typename(Class t) {
String brackets = "";
while (t.isArray()) {
brackets += "[]";
t = t.getComponentType();
}
String name = t.getName();
int pos = name.lastIndexOf('.');
if (pos != -1)
name = name.substring(pos + 1);
return name + brackets;
}
/** Return a string version of modifiers, handling spaces nicely. */
public static String modifiers(int m) {
if (m == 0)
return "";
else
return Modifier.toString(m) + " ";
}
/** Print the modifiers, type, and name of a field */
public static void print_field(Field f) {
System.out.println(" " + modifiers(f.getModifiers()) + typename(f.getType()) + " "
+ f.getName() + ";");
}
/**
* Print the modifiers, return type, name, parameter types and exception type
* of a method or constructor. Note the use of the Member interface to allow
* this method to work with both Method and Constructor objects
*/
public static void print_method_or_constructor(Member member) {
Class returntype = null, parameters[], exceptions[];
if (member instanceof Method) {
Method m = (Method) member;
returntype = m.getReturnType();
parameters = m.getParameterTypes();
exceptions = m.getExceptionTypes();
System.out.print(" " + modifiers(member.getModifiers()) + typename(returntype) + " "
+ member.getName() + "(");
} else {
Constructor c = (Constructor) member;
parameters = c.getParameterTypes();
exceptions = c.getExceptionTypes();
System.out.print(" " + modifiers(member.getModifiers()) + typename(c.getDeclaringClass())
+ "(");
}
for (int i = 0; i < parameters.length; i++) {
if (i > 0)
System.out.print(", ");
System.out.print(typename(parameters[i]));
}
System.out.print(")");
if (exceptions.length > 0)
System.out.print(" throws ");
for (int i = 0; i < exceptions.length; i++) {
if (i > 0)
System.out.print(", ");
System.out.print(typename(exceptions[i]));
}
System.out.println(";");
}
}
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