Understanding logic in CaseInsensitiveComparator

by

From Unicode Technical Standard:

In addition, because of the vagaries of natural language, there are situations where two different Unicode characters have the same uppercase or lowercase

So, it’s not enough to compare only uppercase of two characters, because they may have different uppercase and same lowercase

Simple brute force check gives some results. Check for example code points 73 and 304:

char ch1 = (char) 73; //LATIN CAPITAL LETTER I
char ch2 = (char) 304; //LATIN CAPITAL LETTER I WITH DOT ABOVE
System.out.println(ch1==ch2);
System.out.println(Character.toUpperCase(ch1)==Character.toUpperCase(ch2));
System.out.println(Character.toLowerCase(ch1)==Character.toLowerCase(ch2));

Output:

false
false
true

So “İ” and “I” are not equal to each other. Both characters are uppercase. But they share the same lower case letter: “i” and that gives a reason to treat them as same values in case insensitive comparison.

More Related Contents:

  1. foo(int) is not applicable for the arguments (String)
  2. Replace a character specific number of times in String Java
  3. Java; Initializing A Count of Input, After Period Is Entered
  4. Difference between String replace() and replaceAll()
  5. Splitting a string at every n-th character
  6. How can I check if a single character appears in a string?
  7. Why is the String class declared final in Java?
  8. In Java, how do I check if a string contains a substring (ignoring case)? [duplicate]
  9. How to set classpath when I use javax.tools.JavaCompiler compile the source?
  10. Check and extract a number from a String in Java
  11. When are Java Strings interned?
  12. Why are strings immutable in many programming languages? [duplicate]
  13. String parsing in Java with delimiter tab “\t” using split
  14. Scanner only reads first word instead of line
  15. Create a string with n characters
  16. Convert String XML fragment to Document Node in Java
  17. Why does appending “” to a String save memory?
  18. Best way to concatenate List of String objects? [duplicate]
  19. Convert JsonObject to String
  20. Convert a string to a GregorianCalendar
  21. String gets assigned to a List without a compilation error [duplicate]
  22. Why is String.length() a method?
  23. Is it possible to change the text color in a string to multiple colors in Java?
  24. Java compressing Strings
  25. Java String ReplaceAll method giving illegal repetition error?
  26. Unable to print russian characters
  27. Using DocumentFilter.FilterBypass
  28. Can we access or query the Java String intern (constant) pool?
  29. Java printf using variable field size?
  30. Extract digits from string – StringUtils Java

Leave a Comment