Java String ignore case implementation [duplicate]

Question

I was reading java.lang.String equals ignore case implementation and trying figure out why is there a lower case compare after upper case is already compared? Are there languages where this matters ,where upper cases may not match but lower cases may match?

// Code from java.lang.String class 
  public boolean regionMatches(boolean paramBoolean, int paramInt1, String paramString, int paramInt2, int paramInt3) {
    char[] arrayOfChar1 = this.value;
    int i = paramInt1;
    char[] arrayOfChar2 = paramString.value;
    int j = paramInt2;
    if (paramInt2 < 0 || paramInt1 < 0 || paramInt1 > this.value.length - paramInt3 || paramInt2 > paramString.value.length - paramInt3)
      return false; 
    while (paramInt3-- > 0) {
      char c1 = arrayOfChar1[i++];
      char c2 = arrayOfChar2[j++];
      if (c1 == c2)
        continue; 
      if (paramBoolean) {
        char c3 = Character.toUpperCase(c1);
        char c4 = Character.toUpperCase(c2);
// Why is java comparing to Lower case here
        if (c3 == c4 || Character.toLowerCase(c3) == Character.toLowerCase(c4))
          continue; 
      } 
      return false;
    } 
    return true;
  }

Answer 1

Some characters exist only in lower case, some only exist in upper case. For example, in Germany we have the character "ß" which is lower case. There is no upper case version of it.

I assume that the same can happen in the opposite direction in other languages.