unicode与string之间的相互转换

unicode码对每一个字符用4位16进制数表示。具体规则是：将一个字符(char)的高8位与低8位分别取出，转化为16进制数， 如果转化的16进制数的长度不足2位，则在其后补0，然后将高、低8位转成的16进制字符串拼接起来并在前面补上"\u"
即可。 

方法一：转换原理代码实现

/**
* 将字符串转成unicode
* @param str 待转字符串
* @return unicode字符串
*/
public String convert(String str)
{
str = (str == null ? "" : str);
String tmp;
StringBuffer sb = new StringBuffer(1000);
char c;
int i, j;
sb.setLength(0);
for (i = 0; i < str.length(); i++)
{
c = str.charAt(i);
sb.append("\\u");
j = (c >>>8); //取出高8位
tmp = Integer.toHexString(j);
if (tmp.length() == 1)
sb.append("0");
sb.append(tmp);
j = (c & 0xFF); //取出低8位
tmp = Integer.toHexString(j);
if (tmp.length() == 1)
sb.append("0");
sb.append(tmp);

}
return (new String(sb));
}
/**
* 将unicode 字符串
* @param str 待转字符串
* @return 普通字符串
*/
public String revert(String str)
{
str = (str == null ? "" : str);
if (str.indexOf("\\u") == -1)//如果不是unicode码则原样返回
return str;

StringBuffer sb = new StringBuffer(1000);

for (int i = 0; i <=str.length() - 6;)
{
String strTemp = str.substring(i, i + 6);
String value = strTemp.substring(2);
int c = 0;
for (int j = 0; j < value.length(); j++)
{
char tempChar = value.charAt(j);
int t = 0;
switch (tempChar)
{
case 'a':
t = 10;
break;
case 'b':
t = 11;
break;
case 'c':
t = 12;
break;
case 'd':
t = 13;
break;
case 'e':
t = 14;
break;
case 'f':
t = 15;
break;
default:
t = tempChar - 48;
break;
}

c += t * ((int) Math.pow(16, (value.length() - j - 1)));
}
sb.append((char) c);
i = i + 6;
}
return sb.toString();
}

方法二：api实现

/**
* 字符串转换unicode
*/
public static String convert(String string) {

StringBuffer unicode = new StringBuffer();

for (int i = 0; i < string.length(); i++) {

// 取出每一个字符
char c = string.charAt(i);

// 转换为unicode
unicode.append(String.format("\\u%04x",Integer.valueOf(c)));
}

return unicode.toString();
}
/**
* unicode 转字符串
*/
public static String revert(String unicode) {

StringBuffer string = new StringBuffer();

String[] hex = unicode.split("\\\\u");

for (int i = 1; i < hex.length; i++) {

// 转换出每一个代码点
int data = Integer.parseInt(hex[i], 16);

// 追加成string
string.append((char) data);
}

return string.toString();
}