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Sorting should have been easy. You likely arranged the words into dictionary order, as below.

Lexicographic Order

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To put items in order, there must be a way to compare two items. With strings, the usual order is Lexicographic Order. This is dictionary order, except that all the uppercase letters preceed all the lowercase letters. This order is what the compareTo() method of class String uses.

Two strings are lexicographically equal if they are the same length and contain the same characters in the same positions. In this case, stringA.compareTo( stringB ) returns 0.

Otherwise, stringA.compareTo( stringB ) returns a negative value if StringA comes first and a positive value if StringB comes first.

Memory Aid: think of the strings in a dictionary as arranged from smallest to largest. Then stringA - stringB would produce a negative values if stringA came before StringB.

To determine which string comes first, compare corresponding characters of the two strings from left to right. The first character where the two strings differ determines which string comes first. Characters are compared using the Unicode character set. All uppercase letters come before lower case letters. If two letters are the same case, then alphabetic order is used to compare them.

If two strings contain the same characters in the same positions, then the shortest string comes first.

  Relation   stringA.compareTo( stringB )
stringA Less Than stringB Negative Integer
stringA Equal stringB Zero
stringA Greater Than stringB Positive Integer

Expression Evaluates to Explanation
"Zebra".compareTo("ant") Negative Integer upper case 'Z' comes before lower case 'a'
"Apple".compareTo("apple") Negative Integer upper case 'A' comes before lower case 'a'
"apple".compareTo("orange") Negative Integer 'a' comes before 'o'
"maple".compareTo("morning") Negative Integer 'a' comes before 'o'
"apple".compareTo("apple") Zero same length, same characters in same positions
"orange".compareTo("apple") Positive Integer 'o' comes after 'a'
"applecart".compareTo("apple") Positive Integer longer string "applecart" comes after "apple"
"albatross".compareTo("albany") Positive Integer 't' comes after 'n'

This is slightly confusing. Notice that stringA.compareTo( stringB ) returns a negative integer when stringA and stringB are in the correct order.


Which comes first, "Dog" or "doghouse" ?