android/java中把对象、对象bean、Collection以及字符串转换成Json格式数据

package com.kegao.nearby.bae;

import java.util.Collection;

import java.util.Map;

import java.util.Set;

public class JsonConver {

static String map2Json(Map<String, Object> map) {
if (map.isEmpty())
return "{}";
StringBuilder sb = new StringBuilder(map.size() << 4);
sb.append('{');
Set<String> keys = map.keySet();
for (String key : keys) {
Object value = map.get(key);
sb.append('\"');
sb.append(key);
sb.append('\"');
sb.append(':');
sb.append(toJson(value));
sb.append(',');
}
// 将最后的 ',' 变为 '}':
sb.setCharAt(sb.length() - 1, '}');
return sb.toString();
}

public static String toJson(Object object) {
if (object == null)
return "null";
if (object instanceof String)
return string2Json((String) object);
if (object instanceof Boolean)
return boolean2Json((Boolean) object);
if (object instanceof Number)
return number2Json((Number) object);
if (object instanceof Map)
return map2Json((Map<String, Object>) object);
if (object instanceof Object[])
return array2Json((Object[]) object);
if (object instanceof Collection) //List  Set  

            return collection2Json((Collection) object);  

        throw new RuntimeException("Unsupported type: "+ object.getClass().getName());
}

static String number2Json(Number number) {
return number.toString();
}
/** 

     * 将 Collection 编码为 JSON 格式 (List,Set) 

     *  

     * @param c 

     * @return 

     */  

    static String collection2Json(final Collection<Object> c)  

    {  

        final Object[] arrObj = c.toArray();  

        return toJson(arrObj);  

    }  

static String string2Json(String s) {
StringBuilder sb = new StringBuilder(s.length() + 20);
sb.append('\"');
for (int i = 0; i < s.length(); i++) {
char c = s.charAt(i);
switch (c) {
case '\"':
sb.append("\\\"");
break;
case '\\':
sb.append("\\\\");
break;
case '/':
sb.append("\\/");
break;
case '\b':
sb.append("\\b");
break;
case '\f':
sb.append("\\f");
break;
case '\n':
sb.append("\\n");
break;
case '\r':
sb.append("\\r");
break;
case '\t':
sb.append("\\t");
break;
default:
sb.append(c);
}
}
sb.append('\"');
return sb.toString();
}

static String boolean2Json(Boolean bool) {
return bool.toString();
}

static String array2Json(Object[] array) {
if (array.length == 0)
return "[]";
StringBuilder sb = new StringBuilder(array.length << 4);
sb.append('[');
for (Object o : array) {
sb.append(toJson(o));
sb.append(',');
}
// 将最后添加的 ',' 变为 ']':
sb.setCharAt(sb.length() - 1, ']');
return sb.toString();
}

}