本人新手，刚开始看《Java核心技术》，书中讲了可供任意类使用的通用toString方法，其中使用getDeclaredFields获得所有的数据域，然后使用setAccessible将所有的域设置成可访问的。对于每个域，获得了名字和值。递归调用toString方法，将每个值转换成字符串。
代码如下：
import java.lang.reflect.*;
import java.util.*;
/**
* 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>();
}
代码的输出是：
java.util.ArrayList[elementData=class java.lang.Object[]{java.lang.Integer[value=1][][],java.lang.Integer[value=4][][],java.lang.Integer[value=9][][],java.lang.Integer[value=16][][],java.lang.Integer[value=25][][],null,null,null,null,null},size=5][modCount=5][][]
这输出我看不明白啊，红色部分是哪来的，value又是哪来的，还有[][]和那5个null。问题多多，勿笑
