短視訊帶貨原始碼，對於輸入的驗證碼，不區分大小寫

適用於驗證碼校驗（不區分大小寫）

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 {
        @JvmStatic
        fun 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))
        }
    }
}

​執行結果

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

原始碼

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

1、優先判斷記憶體地址值是否一致：this == anotherString

2、不為null且長度一致的情況下： 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、判斷是否陣列越界
        if ((ooffset < 0) || (toffset < 0)
                || (toffset > (long)value.length - len)
                || (ooffset > (long)other.value.length - len)) {
            return false;
        }
        //2、迴圈遍歷char是否一致
        while (len-- > 0) {
            char c1 = ta[to++];
            char c2 = pa[po++];
            if (c1 == c2) {
                continue;
            }
            if (ignoreCase) {//是否忽略大小寫，true 則同義轉換為大寫或同義轉換為小寫進行校驗
                // 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;
    }

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