Structuring Data with Java - Java - page 264

Solution

Use the static method Arrays.sort() or Collections.sort() , optionally providing a Com-
parator .

Discussion

If your data is in an array, then you can sort it using the static sort() method of the Arrays
utility class. If it is in a Collection , you can use the static sort() method of the Collec-
tions class. Here is a set of strings being sorted in-place in an Array :

public public class class SortArray SortArray {

public public static void main ( String [] unused ) {

String [] strings = {
"painful" ,
"mainly" ,
"gaining" ,
"raindrops"

static void

};
Arrays . sort ( strings );
for for ( int int i = 0 ; i < strings . length ; i ++) {

System . out . println ( strings [ i ]);

}

}

}

What if the default sort order isn't what you want? Well, you can create an object that imple-
ments the Comparator<T> interface and pass that as the second argument to sort. For-
tunately, for the most common ordering next to the default, you don't have to: a public con-
stant String.CASE_INSENSITIVE_ORDER can be passed as this second argument. The
String class defines it as “a Comparator<String> that orders String objects as by com-
pareToIgnoreCase .” But if you need something fancier, you probably need to write a Com-
parator<T> . Suppose that, for some strange reason, you need to sort strings using all but the
first character of the string. One way to do this would be to write this Comparator<String> :

/** Comparator for comparing strings ignoring first character.
*/
public public class class SubstringComparator SubstringComparator implements implements Comparator < String > {

@Override
public

public int int compare ( String s1 , String s2 ) {