java过滤字符串中的特殊字符

public static String toHtmlString(String str) { 
if (str == null || ("").equals(str.trim())) { 
return ""; 
} 

StringBuffer stringbuffer = new StringBuffer(); 
int j = str.length(); 

for (int i = 0; i < j; i++) { 
char c = str.charAt(i); 

switch (c) { 
case 39: // ' 
stringbuffer.append("&acute;"); 
break; 
case 60: // < 
stringbuffer.append("&lt;"); 
break; 
case 62: // > 
stringbuffer.append("&gt;"); 
break; 
case 38: // & 
stringbuffer.append("&amp;"); 
break; 
case 34: // " 
stringbuffer.append("&quot;"); 
break; 
case 13: 
if (i < j - 1 && str.charAt(i + 1) == 10) { 
stringbuffer.append("<br>"); 
i++; 
} 
break; 
case 32: 
stringbuffer.append("&nbsp"); 
break; 
default: 
stringbuffer.append(c); 
break; 
} 
} 
return new String(stringbuffer.toString()); 
}