编码知识介绍.pptx

Encoding;传说中： 纯文本 = ASCII = 字符是8位 ??? ;American Standard Code for Information Interchange 7位，128个字符。 例子 Value 意义 7 BEL 48 0 63 ? 65 A 97 a;4;0x00 to 0x1F 控制字符 32个 0x20 to 0x7E 可打印字符 95个 0X7F delete ;ASCII Art; @Test public void testASCII() throws Exception { String oldString = abcd; //字符串转为字节流，又转回为字符串。 True(testString2Byte2String(oldString, Encoding.US_ASCII)); oldString = abcd信之; False(testString2Byte2String(oldString, Encoding.US_ASCII)); };String - Bytes - String encoding = US-ASCII bytes[] = // 16进制表示 97,98,99,100, // 无符号整型表示 oldString = abcd newString = abcd equals = true String - Bytes - String encoding = US-ASCII bytes[] = 616263643F3F 97,98,99,100,63,63, oldString = abcd信之 newString = abcd?? equals = false ASCII无法存储中文，直接解释为63(???)，一般看到???，很多是编码问题。;1 byte = 8 bits 有1个bit处于空闲。 各种代码页。单字节代码页，双字节代码页。 混乱！ ;不是ASCII标准的扩展标准 不是单一的一套字符集 一般和ASCII兼容 ;又名Latin-1 8-bit single-byte coded graphic character sets 主要服务目标 Western European 语言 兼容ASCII ISO/IEC 8859 is a joint ISO and IEC series of standards for 8-bit character encodings. ISO 8859-1是其中应用最广泛的一套标准。 ;String - Bytes - String encoding = ISO-8859-1 bytes[] = 97,98,99,100, oldString = abcd newString = abcd equals = true String - Bytes - String encoding = ISO-8859-1 bytes[] = 616263643F3F 97,98,99,100,63,63, oldString = abcd信之 newString = abcd?? equals = false;String - Bytes - String encoding = ISO-8859-1 bytes[] = B1 177, oldString = ± newString = ± equals = true;Uni 单一 Unicode 终极单一编码方案 每个字符16bits, 共2^16=65536个字符???;传说中 A 0100 0001 Unicode中 A U+0041 代码点 --- 抽象的东西，不涉及存储。;Unicode defines a code space of 1,114,112 code points in the range 0x000000 to 0x10FFFF. 划分为17个Unicode plane. Plane 0:Basic Multilingual Plane (BMP) 0000-FFFF Plane 1-16: Supplementary Planes [1-10]0000 – [1-10]FFFF 不是