public static boolean isAsciiAlphanumeric(char ch) {
        return (ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z') || (ch >= '0' && ch <= '9');
    }
<p>Checks whether the character is ASCII 7 bit numeric.</p>

<pre>
  CharUtils.isAsciiAlphanumeric('a')  = true
  CharUtils.isAsciiAlphanumeric('A')  = true
  CharUtils.isAsciiAlphanumeric('3')  = true
  CharUtils.isAsciiAlphanumeric('-')  = false
  CharUtils.isAsciiAlphanumeric('\n') = false
  CharUtils.isAsciiAlphanumeric('&copy;') = false
</pre>

@param ch  the character to check
@return true if between 48 and 57 or 65 and 90 or 97 and 122 inclusive
android/android_framework/base/src/main/java/lang3/CharUtils.java