Java核心技术很优美的代码2 "万能的"toString

/**
@version 1.11 2004-02-21
@author Cay Horstmann
*/

import java.lang.reflect.*;
import java.util.*;
import java.text.*;

public class ObjectAnalyzerTest
{
public static void main(String[] args)
{
ArrayList<Integer> squares = new ArrayList<Integer>();
for (int i = 1; i <= 5; i++) squares.add(i * i);
System.out.println(new ObjectAnalyzer().toString(squares));
}
}

class ObjectAnalyzer
{
/**
Converts an object to a string representation that lists
all fields.
@param obj an object
@return a string with the object's class name and all
field names and values
*/
public String toString(Object obj)
{
if (obj == null) return "null";
if (visited.contains(obj)) return "...";
visited.add(obj);
Class cl = obj.getClass();
if (cl == String.class) return (String) obj;
if (cl.isArray())
{
String r = cl.getComponentType() + "[]{";
for (int i = 0; i < Array.getLength(obj); i++)
{
if (i > 0) r += ",";
Object val = Array.get(obj, i);
if (cl.getComponentType().isPrimitive()) r += val;
else r += toString(val);
}
return r + "}";
}

String r = cl.getName();
// inspect the fields of this class and all superclasses
do
{
r += "[";
Field[] fields = cl.getDeclaredFields();
AccessibleObject.setAccessible(fields, true);
// get the names and values of all fields
for (Field f : fields)
{
if (!Modifier.isStatic(f.getModifiers()))
{
if (!r.endsWith("[")) r += ",";
r += f.getName() + "=";
try
{
Class t = f.getType();
Object val = f.get(obj);
if (t.isPrimitive()) r += val;
else r += toString(val);
}
catch (Exception e) { e.printStackTrace(); }
}
}
r += "]";
cl = cl.getSuperclass();
}
while (cl != null);

return r;
}

private ArrayList<Object> visited = new ArrayList<Object>();
}