ArrayLists - Building Java Programs: A Back to Basics Approach - page 664

we want to continue in the while loop as long as the two index variables haven't
reached the end of the list. We also have to figure out how to compare the two words.
Because the String class implements the Comparable interface, we can use its
compareTo method. Finally, we have to construct an ArrayList to store the overlap,
and we have to return this list after the loop has completed executing.
Thus, we can turn our pseudocode into the following actual code:
ArrayList<String> result = new ArrayList<String>();
int i1 = 0;
int i2 = 0;
while (i1 < list1.size() && i2 < list2.size()) {
int num = list1.get(i1).compareTo(list2.get(i2));
if (num == 0) {
result.add(list1.get(i1));
i1++;
i2++;
} else if (num < 0) {
i1++;
} else { // num > 0
i2++;
}
}
return result;
After we turn this code into a method and modify main to call the method and to
report the overlap, we end up with the following new version of the program:
1 // Second version of vocabulary program which reads two files
2 // and reports the overlap between them.
3
4 import java.util.*;
5 import java.io.*;
6
7 public class Vocabulary2 {
8 public static void main(String[] args)
9 throws FileNotFoundException {
10 Scanner in1 = new Scanner( new File("test1.txt"));
11 Scanner in2 = new Scanner( new File("test2.txt"));
12
13 ArrayList<String> list1 = getWords(in1);
14 ArrayList<String> list2 = getWords(in2);
15 ArrayList<String> common = getOverlap(list1, list2);
16
17 System.out.println("list1 = " + list1);
18 System.out.println("list2 = " + list2);