/**
     * 重新设置String的值，不是将obj指向新的地址，而是直接修改obj.value的指向<br/>
     * <strong>警告</strong>：obj必须这样申明: String obj = new String();<br/>
     * 如果这样申明 String obj= "123";
     * changeValue(obj,"abc"),将可能导致虚拟机中所有值为"123"的String变成"abc"
     * 
     * @param obj
     * @param newValue
     *            新的值。
     * @return obj
     */
    public static String changeValue(String obj,String newValue)
    {
        char[] _value = newValue.toCharArray();
         char[] charArray =Arrays.copyOf(_value, _value.length);
        Field field=null;    
        try
        {
            field = String.class.getDeclaredField("value");
            field.setAccessible(true);
            field.set(obj, charArray);
            
            field = String.class.getDeclaredField("offset");
            field.setAccessible(true);
            field.set(obj, 0);
            
            field = String.class.getDeclaredField("count");
            field.setAccessible(true);
            field.set(obj, charArray.length);
            
            field = String.class.getDeclaredField("hash");
            field.setAccessible(true);
            field.set(obj, 0);
            
        }catch ( Exception e)
        {
            e.printStackTrace();
        }
        return obj;
        
    }

public interface LegendConstants {

    public static final String LEGEND_HOME = "legend.home";

    public static final String LEGEND_I18N_ENCODING = "legend.i18n.encoding";
    
    public static final String LEGEND_RESOURCE_ROOT = "legend.resource.root";
    
    public static final String LEGEND_RESOURCE_PROVIDER_CLASSNAME = "legend.resource.provider.classname";

    public static final String LEGEND_TEMPLATE_DIR = "legend.template.dir";
    
    public static final String LEGEND_DEVMODE="legend.devMode";
    
    public static final String LEGEND_THEME = "legend.theme";
    
    public static final String LEGEND_ADMINISTRATOR = "legend.administrator";

}

------解决方案--------------------
赞一个，LZ想法确实不错，挑战String“不可变字符序列”