验证码校验：String.equalsIgnoreCase()

适用于验证码校验（不区分大小写）

public class TestString {public static void main(String[] args) {testEquals("asd", "asd");testEquals("asD", "Asd");}/*** @see java.lang.String#equalsIgnoreCase* usage: checking vertification code*/private static void testEquals(String a, String b) {System.out.println("\"" + a + "\".equals(\"" + b + "\") = " + a.equals(b));System.out.println("\"" + a + "\".equalsIgnoreCase(\"" + b + "\") = " + a.equalsIgnoreCase(b));}
}

class TestString {companion object {@JvmStaticfun main(args: Array<String>) {testEquals("asd", "asd")testEquals("asD", "Asd")}private fun testEquals(a: String, b: String) {println("\"$a\".equals(\"$b\") = " + (a == b))println("\"$a\".equalsIgnoreCase(\"$b\") = " + a.equals(b, ignoreCase = true))}}
}

运行结果

"asd".equals("asd") = true
"asd".equalsIgnoreCase("asd") = true
"asD".equals("Asd") = false
"asD".equalsIgnoreCase("Asd") = true

源码

    public boolean equalsIgnoreCase(String anotherString) {return (this == anotherString) ? true: (anotherString != null)&& (anotherString.value.length == value.length)&& regionMatches(true, 0, anotherString, 0, value.length);}

1、优先判断内存地址值是否一致：this == anotherString
2、不为null且长度一致的情况下： regionMatches(true, 0, anotherString, 0, value.length)

public boolean regionMatches(boolean ignoreCase, int toffset,String other, int ooffset, int len) {char ta[] = value;int to = toffset;char pa[] = other.value;int po = ooffset;// Note: toffset, ooffset, or len might be near -1>>>1.//1、判断是否数组越界if ((ooffset < 0) || (toffset < 0)|| (toffset > (long)value.length - len)|| (ooffset > (long)other.value.length - len)) {return false;}//2、循环遍历char是否一致while (len-- > 0) {char c1 = ta[to++];char c2 = pa[po++];if (c1 == c2) {continue;}if (ignoreCase) {//是否忽略大小写，true 则同义转换为大写或同义转换为小写进行校验// If characters don't match but case may be ignored,// try converting both characters to uppercase.// If the results match, then the comparison scan should// continue.char u1 = Character.toUpperCase(c1);char u2 = Character.toUpperCase(c2);if (u1 == u2) {continue;}// Unfortunately, conversion to uppercase does not work properly// for the Georgian alphabet, which has strange rules about case// conversion.  So we need to make one last check before// exiting.if (Character.toLowerCase(u1) == Character.toLowerCase(u2)) {continue;}}return false;}return true;}

小写字母转换大写字母

    public static char toUpperCase(char ch) {return (char)toUpperCase((int)ch);}

    public static int toUpperCase(int codePoint) {return CharacterData.of(codePoint).toUpperCase(codePoint);}

** testEquals(“asD”, “Asd”);
char ‘a’ = 97 ,char ‘A’=65,ch >>>8 == 0 为 true**

    static final CharacterData of(int ch) {if (ch >>> 8 == 0) {     // fast-pathreturn CharacterDataLatin1.instance;} else {switch(ch >>> 16) {  //plane 00-16case(0):return CharacterData00.instance;case(1):return CharacterData01.instance;case(2):return CharacterData02.instance;case(14):return CharacterData0E.instance;case(15):   // Private Usecase(16):   // Private Usereturn CharacterDataPrivateUse.instance;default:return CharacterDataUndefined.instance;}}}

CharacterDataLatin1.instance

小写字母转大写字母

    int toUpperCase(int ch) {int mapChar = ch;int val = getProperties(ch);if ((val & 0x00010000) != 0) {if ((val & 0x07FC0000) != 0x07FC0000) {int offset = val  << 5 >> (5+18);mapChar =  ch - offset;} else if (ch == 0x00B5) {mapChar = 0x039C;}}return mapChar;}

大写字母转小写字母

    int toLowerCase(int ch) {int mapChar = ch;int val = getProperties(ch);if (((val & 0x00020000) != 0) && ((val & 0x07FC0000) != 0x07FC0000)) { int offset = val << 5 >> (5+18);mapChar = ch + offset;}return mapChar;}

    int getProperties(int ch) {char offset = (char)ch;int props = A[offset];return props;}

    static {{ // THIS CODE WAS AUTOMATICALLY CREATED BY GenerateCharacter:char[] data = A_DATA.toCharArray();assert (data.length == (256 * 2));int i = 0, j = 0;while (i < (256 * 2)) {int entry = data[i++] << 16;A[j++] = entry | data[i++];}}}   static final int A[] = new int[256];static final String A_DATA ="\u4800\u100F\u4800\u100F\u4800\u100F\u4800\u100F\u4800\u100F\u4800\u100F\u4800"+"\u100F\u4800\u100F\u4800\u100F\u5800\u400F\u5000\u400F\u5800\u400F\u6000\u400F"+"\u5000\u400F\u4800\u100F\u4800\u100F\u4800\u100F\u4800\u100F\u4800\u100F\u4800"+"\u100F\u4800\u100F\u4800\u100F\u4800\u100F\u4800\u100F\u4800\u100F\u4800\u100F"+"\u4800\u100F\u4800\u100F\u5000\u400F\u5000\u400F\u5000\u400F\u5800\u400F\u6000"+"\u400C\u6800\030\u6800\030\u2800\030\u2800\u601A\u2800\030\u6800\030\u6800"+"\030\uE800\025\uE800\026\u6800\030\u2000\031\u3800\030\u2000\024\u3800\030"+"\u3800\030\u1800\u3609\u1800\u3609\u1800\u3609\u1800\u3609\u1800\u3609\u1800"+"\u3609\u1800\u3609\u1800\u3609\u1800\u3609\u1800\u3609\u3800\030\u6800\030"+"\uE800\031\u6800\031\uE800\031\u6800\030\u6800\030\202\u7FE1\202\u7FE1\202"+"\u7FE1\202\u7FE1\202\u7FE1\202\u7FE1\202\u7FE1\202\u7FE1\202\u7FE1\202\u7FE1"+"\202\u7FE1\202\u7FE1\202\u7FE1\202\u7FE1\202\u7FE1\202\u7FE1\202\u7FE1\202"+"\u7FE1\202\u7FE1\202\u7FE1\202\u7FE1\202\u7FE1\202\u7FE1\202\u7FE1\202\u7FE1"+"\202\u7FE1\uE800\025\u6800\030\uE800\026\u6800\033\u6800\u5017\u6800\033\201"+"\u7FE2\201\u7FE2\201\u7FE2\201\u7FE2\201\u7FE2\201\u7FE2\201\u7FE2\201\u7FE2"+"\201\u7FE2\201\u7FE2\201\u7FE2\201\u7FE2\201\u7FE2\201\u7FE2\201\u7FE2\201"+"\u7FE2\201\u7FE2\201\u7FE2\201\u7FE2\201\u7FE2\201\u7FE2\201\u7FE2\201\u7FE2"+"\201\u7FE2\201\u7FE2\201\u7FE2\uE800\025\u6800\031\uE800\026\u6800\031\u4800"+"\u100F\u4800\u100F\u4800\u100F\u4800\u100F\u4800\u100F\u4800\u100F\u5000\u100F"+"\u4800\u100F\u4800\u100F\u4800\u100F\u4800\u100F\u4800\u100F\u4800\u100F\u4800"+"\u100F\u4800\u100F\u4800\u100F\u4800\u100F\u4800\u100F\u4800\u100F\u4800\u100F"+"\u4800\u100F\u4800\u100F\u4800\u100F\u4800\u100F\u4800\u100F\u4800\u100F\u4800"+"\u100F\u4800\u100F\u4800\u100F\u4800\u100F\u4800\u100F\u4800\u100F\u4800\u100F"+"\u3800\014\u6800\030\u2800\u601A\u2800\u601A\u2800\u601A\u2800\u601A\u6800"+"\034\u6800\030\u6800\033\u6800\034\000\u7005\uE800\035\u6800\031\u4800\u1010"+"\u6800\034\u6800\033\u2800\034\u2800\031\u1800\u060B\u1800\u060B\u6800\033"+"\u07FD\u7002\u6800\030\u6800\030\u6800\033\u1800\u050B\000\u7005\uE800\036"+"\u6800\u080B\u6800\u080B\u6800\u080B\u6800\030\202\u7001\202\u7001\202\u7001"+"\202\u7001\202\u7001\202\u7001\202\u7001\202\u7001\202\u7001\202\u7001\202"+"\u7001\202\u7001\202\u7001\202\u7001\202\u7001\202\u7001\202\u7001\202\u7001"+"\202\u7001\202\u7001\202\u7001\202\u7001\202\u7001\u6800\031\202\u7001\202"+"\u7001\202\u7001\202\u7001\202\u7001\202\u7001\202\u7001\u07FD\u7002\201\u7002"+"\201\u7002\201\u7002\201\u7002\201\u7002\201\u7002\201\u7002\201\u7002\201"+"\u7002\201\u7002\201\u7002\201\u7002\201\u7002\201\u7002\201\u7002\201\u7002"+"\201\u7002\201\u7002\201\u7002\201\u7002\201\u7002\201\u7002\201\u7002\u6800"+"\031\201\u7002\201\u7002\201\u7002\201\u7002\201\u7002\201\u7002\201\u7002"+"\u061D\u7002";

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