package example.encoding;
import java.io.UnsupportedEncodingException;
/** *//**
* The Class GetCharTest.
*/
public class GetCharTest {
/** *//**
* The main method.
*
* @param args the arguments
*/
public static void main(String args[]) {
String content = "中文";
String defaultEncoding = System.getProperty("file.encoding");
String defaultLnaguage = System.getProperty("user.language");
System.out.println("System default encoding --- " + defaultEncoding);
System.out.println("System default language --- " + defaultLnaguage);
GetCharTest tester = new GetCharTest();
tester.getCharWithDefaultEncoding(content);
tester.getCharWithGivenEncoding(content, "ISO-8859-1");
tester.getCharWithGivenEncoding(content, "GBK");
tester.getCharWithGivenEncoding(content, "UTF-8");
}
/** *//**
* Gets the char with default encoding.
*
* @param content the content
*
* @return the char with default encoding
*/
public void getCharWithDefaultEncoding(String content) {
System.out.println("\nGet characters with default encoding\n");
printCharArray(content);
}
/** *//**
* Gets the char with given encoding.
*
* @param content the content
* @param encoding the encoding
*
* @return the char with given encoding
*/
public void getCharWithGivenEncoding(String content, String encoding) {
System.out.println("\nGet characters with given encoding : " + encoding
+ "\n");
try {
String encodedString = new String(content.getBytes(), encoding);
printCharArray(encodedString);
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
}
/** *//**
* Prints the char array.
*
* @param inStr the in str
*/
public void printCharArray(String inStr) {
char[] charArray = inStr.toCharArray();
for (int i = 0; i < inStr.length(); i++) {
byte b = (byte) charArray[i];
short s = (short) charArray[i];
String hexB = Integer.toHexString(b).toUpperCase();
String hexS = Integer.toHexString(s).toUpperCase();
StringBuffer sb = new StringBuffer();
// print char
sb.append("char[");
sb.append(i);
sb.append("]='");
sb.append(charArray[i]);
sb.append("'\t");
// byte value
sb.append("byte=");
sb.append(b);
sb.append(" \\u");
sb.append(hexB);
sb.append('\t');
// short value
sb.append("short=");
sb.append(s);
sb.append(" \\u");
sb.append(hexS);
sb.append('\t');
// Unicode Block
sb.append(Character.UnicodeBlock.of(charArray[i]));
System.out.println(sb.toString());
}
System.out.println("\nCharacters length: " + charArray.length);
}
}
【1】在中文平台下,测试的结果如下:
System default encoding --- GBK
System default language --- zh
Get characters with default encoding
char[0]='中' byte=45 \u2D short=20013 \u4E2D CJK_UNIFIED_IDEOGRAPHS
char[1]='文' byte=-121 \uFFFFFF87 short=25991 \u6587 CJK_UNIFIED_IDEOGRAPHS
Characters length: 2
Get characters with given encoding : ISO-8859-1
char[0]='?' byte=-42 \uFFFFFFD6 short=214 \uD6 LATIN_1_SUPPLEMENT
char[1]='?' byte=-48 \uFFFFFFD0 short=208 \uD0 LATIN_1_SUPPLEMENT
char[2]='?' byte=-50 \uFFFFFFCE short=206 \uCE LATIN_1_SUPPLEMENT
char[3]='?' byte=-60 \uFFFFFFC4 short=196 \uC4 LATIN_1_SUPPLEMENT
Characters length: 4
Get characters with given encoding : GBK
char[0]='中' byte=45 \u2D short=20013 \u4E2D CJK_UNIFIED_IDEOGRAPHS
char[1]='文' byte=-121 \uFFFFFF87 short=25991 \u6587 CJK_UNIFIED_IDEOGRAPHS
Characters length: 2
Get characters with given encoding : UTF-8
char[0]='?' byte=-3 \uFFFFFFFD short=-3 \uFFFFFFFD SPECIALS
char[1]='?' byte=-3 \uFFFFFFFD short=-3 \uFFFFFFFD SPECIALS
char[2]='?' byte=-3 \uFFFFFFFD short=-3 \uFFFFFFFD SPECIALS
char[3]='?' byte=-3 \uFFFFFFFD short=-3 \uFFFFFFFD SPECIALS
Characters length: 4
【2】在英文平台下,测试的结果如下:
System default encoding --- Cp1252
System default language --- en
Get characters with default encoding
char[0]='?' byte=45 \u2D short=20013 \u4E2D CJK_UNIFIED_IDEOGRAPHS
char[1]='?' byte=-121 \uFFFFFF87 short=25991 \u6587 CJK_UNIFIED_IDEOGRAPHS
Characters length: 2
Get characters with given encoding : ISO-8859-1
char[0]='?' byte=63 \u3F short=63 \u3F BASIC_LATIN
char[1]='?' byte=63 \u3F short=63 \u3F BASIC_LATIN
Characters length: 2
Get characters with given encoding : GBK
char[0]='?' byte=63 \u3F short=63 \u3F BASIC_LATIN
char[1]='?' byte=63 \u3F short=63 \u3F BASIC_LATIN
Characters length: 2
Get characters with given encoding : UTF-8
char[0]='?' byte=63 \u3F short=63 \u3F BASIC_LATIN
char[1]='?' byte=63 \u3F short=63 \u3F BASIC_LATIN
Characters length: 2
【结论】
和getBytes(encoding)不同,toCharArray()返回的是"自然字符"。但是这个"自然字符"的数目和内容却是由原始的编码方式决定的。来看看里面是如何进行字符串的操作的:
String encodedString = new String(content.getBytes(), encoding);
char[] charArray = inStr.toCharArray();
可以看到系统首先对原始字符串按照默认的编码方式进行编码,得到一个字节数组,然后按照指定的新的编码方式进行解码,得到新的编码后的字符串。再转换成对应的字符数组。
由于在中文平台下,默认的字符集编码是GBK,于是content.getBytes()得到的是什么呢?就是下面这4个字节:
byte[0] = -42 hex string = ffffffd6
byte[1] = -48 hex string = ffffffd0
byte[2] = -50 hex string = ffffffce
byte[3] = -60 hex string = ffffffc4
如果新的encoding是GBK,那么经过解码后,由于一个字符用2个字节表示。于是最终的结果就是:
char[0]='中' --- byte[0] + byte[1]
char[1]='文' --- byte[2] + byte[3]
如果新的encoding是ISO-8859-1,那么经过解码后,由于一个字符用1个字节表示,于是原来本应该2个字节一起解析的变成单个字节解析,每个字节都代表了一个汉字字符的一半。这一半的字节在ISO-8859-1中找不到对应的字符,就变成了"?"了,最终的结果:
char[0]='?' ---- byte[0]
char[1]='?' ---- byte[1]
char[2]='?' ---- byte[2]
char[3]='?' ---- byte[3]
如果新的encoding是UTF-8,那么经过解码后,由于一个字符用3个字节表示,于是原来4个字节的数据无法正常的解析成UTF-8的数据,最终的结果也是每一个都变成"?"。
char[0]='?' ---- byte[0]
char[1]='?' ---- byte[1]
char[2]='?' ---- byte[2]
char[3]='?' ---- byte[3]
如果是在英文平台下,由于默认的编码方式是Cp1252,于是content.getBytes()得到的字节都是被截去一半的残留字符,所以我们看到在英文平台下,不论指定的encoding是GBK、UTF-8,其结果和ISO-8859-1都是一样的。
记住:
这个方法再次证明了String的getBytes()方法的危险性,如果我们使用new String(str.getBytes(), encoding)对字符串进行重新编码解码时,我们一定要清楚str.getBytes()方法返回的字节数组的长度、内容到底是什么,因为在接下来使用新的encoding进行编码解码时,Java并不会自动地对字节数组进行扩展以适应新的encoding。而是按照新的编码方法直接对该字节数组进行解析。
于是结果就像上面的例子一样,同样是4个原始字节,有些每2个一组进行解析,有些每个一组进行解析,有些每3个一组进行解析。其结果就只能看那种编码方式合适了。
posted on 2010-02-22 17:18
Paul Lin 阅读(7073)
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