java各种toString方法

1. java的根类: Object

   /* getClass().getName() + '@' + Integer.toHexString(hashCode())
        * </pre></blockquote>
        *
        * @return  a string representation of the object.
        */
       public String toString() {
   	return getClass().getName() + "@" + Integer.toHexString(hashCode());
       }

    所以我们见到的没有override toString()方法的都会调用Object的toString()方法。
2. 数组：

   		/**
   		 * [I@119298d
   		 */
   		int[] a = {1,2,3};
   		System.out.println(a.toString());
   		/**
   		 * [[I@119298d
   		 */
   		int[][] b = {{1},{2},{3}};
   		System.out.println(b.toString()); 
   

    无法override 数组类的toString()方法，它是由虚拟机在第一次遇到时生成的数组数据类型.
3. String类型
   

       /**
        * This object (which is already a string!) is itself returned.
        *
        * @return  the string itself.
        */
       public String toString() {
   	return this;
       }

4. Set和List

   		/**
   		 * [1, 1, 1, 1]
   		 * [1]
   		 */
   		List list = new ArrayList(Collections.nCopies(4, 1));
   		System.out.println(list.toString());
   		Set set = new TreeSet(Collections.nCopies(4, 1));
   		System.out.println(set.toString());

    这个是由抽象类AbstractCollection实现的toString()方法：

       public String toString() {
           Iterator<E> i = iterator();
   	if (! i.hasNext())
   	    return "[]";
   
   	StringBuilder sb = new StringBuilder();
   	sb.append('[');
   	for (;;) {
   	    E e = i.next();
   	    sb.append(e == this ? "(this Collection)" : e);
   	    if (! i.hasNext())
   		return sb.append(']').toString();
   	    sb.append(", ");
   	}
       }

    
5. Map
   

   		/**
   		 * {}
   		 */
   		Map map = new HashMap();
   		System.out.println(map.toString());

    这个是由抽象类AbstractMap实现的toString()方法：
   

       public String toString() {
   	Iterator<Entry<K,V>> i = entrySet().iterator();
   	if (! i.hasNext())
   	    return "{}";
   
   	StringBuilder sb = new StringBuilder();
   	sb.append('{');
   	for (;;) {
   	    Entry<K,V> e = i.next();
   	    K key = e.getKey();
   	    V value = e.getValue();
   	    sb.append(key   == this ? "(this Map)" : key);
   	    sb.append('=');
   	    sb.append(value == this ? "(this Map)" : value);
   	    if (! i.hasNext())
   		return sb.append('}').toString();
   	    sb.append(", ");
   	}
       }

    应该还有比较特殊的，以后慢慢补充，现在只想到这些。