Mega Code Archive
This program uses reflection to spy on objects
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/*
This program is a part of the companion code for Core Java 8th ed.
(http://horstmann.com/corejava)
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
import java.lang.reflect.AccessibleObject;
import java.lang.reflect.Array;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.ArrayList;
/**
* This program uses reflection to spy on objects.
*
* @version 1.11 2004-02-21
* @author Cay Horstmann
*/
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>();
}
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