You can set a collator’s strength to select how selective it should be. Character differences are classified as primary, secondary, tertiary, and identical. For example, in English, the difference between “A” and “Z” is considered primary, the difference between “A” and “Å” is secondary, and between “A” and “a” is tertiary.
By setting the strength of the collator to
Collator.PRIMARY, you tell it to pay attention only to primary differences. By setting the strength to
Collator.SECONDARY, you instruct the collator to take secondary differences into account. That is, two strings will be more likely to be considered different when the strength is set to “secondary” or “tertiary,” as shown in Table 5.4.