Ok,
as the subject of my first post states, This is from Lab 1016(5.2) Sort a
list using Comparator. In that lesson, there is a class named
MyCompartors.class, that class contains a method called stringComparator()
.
1) The first line of that method is a return statement and there is another
one at the bottom of the same stringComparator() method. Why does it have
multiple return statements?
2) The Main.java file calls on the MyComparators.stringComparator(); method,
but never uses the compare(Object o1, Object o2) method which i s the only
method there. Please provide explanation on this.
Code should be available on the Collections labs, but I am attaching them
here anyway.
On Monday, January 6, 2014 2:15:36 PM UTC-5, Deepak A L wrote:
>
> hi.
> how does it work...confused.
>
> attach the working example team of jpassion with correct explanation....
>
> Regards,
> Deepak
> On Jan 6, 2014 12:14 AM, "Sergio G Barreros"
> <[email protected]<javascript:>>
> wrote:
>
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package sortingcomparator;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.Date;
public class Main {
public static void main(String[] args) {
// Create an ArrayList object and add items to it.
ArrayList a1 = new ArrayList();
a1.add("Boston");
a1.add("New York");
a1.add("Seoul");
a1.add("Tokyo");
a1.add("London");
a1.add("Bangkok");
System.out.println("Before sorting = " + a1);
// Get String Comparator object and sort the list
Comparator comp = MyComparators.stringComparator();
Collections.sort(a1, comp);
// Display the sorted list
System.out.println("Sorted list using String Comparator = " + a1);
// Create an ArrayList object and add items to it.
ArrayList a2 = new ArrayList();
a2.add(new Integer(33));
a2.add(new Integer(17));
a2.add(new Integer(45));
a2.add(new Integer(100));
a2.add(new Integer(3));
System.out.println("Before sorting = " + a2);
// Get Integer Comparator object and sort the list
Comparator comp2 = MyComparators.integerComparator();
Collections.sort(a2, comp2);
// Display the sorted list
System.out.println("Sorted list using Integer Comparator = " + a2);
// Create an ArrayList object and add items to it.
ArrayList a3 = new ArrayList();
a3.add(new Date(45785678));
a3.add(new Date(12345678));
a3.add(new Date(23456789));
System.out.println("Before sorting = " + a3);
// Get Integer Comparator object and sort the list
Comparator comp3 = MyComparators.dateComparator();
Collections.sort(a3, comp3);
// Display the sorted list
System.out.println("Sorted list using Integer Comparator = " + a3);
}
}
package sortingcomparator;
import java.util.Comparator;
import java.util.Date;
public class MyComparators {
// String Comparator object
public static Comparator stringComparator() {
return new Comparator() {
public int compare(Object o1, Object o2) {
String s1 = (String)o1;
String s2 = (String)o2;
int len1 = s1.length();
int len2 = s2.length();
int n = Math.min(len1, len2);
char v1[] = s1.toCharArray();
char v2[] = s2.toCharArray();
int pos = 0;
while (n-- != 0) {
char c1 = v1[pos];
char c2 = v2[pos];
if (c1 != c2) {
return c1 - c2;
}
pos++;
}
return len1 - len2;
}
};
}
// Integer Comparator object
public static Comparator integerComparator() {
return new Comparator() {
public int compare(Object o1, Object o2) {
int val1 = ((Integer)o1).intValue();
int val2 = ((Integer)o2).intValue();
return (val1<val2 ? -1 : (val1==val2 ? 0 : 1));
}
};
}
// Date Comparator object
public static Comparator dateComparator() {
return new Comparator() {
public int compare(Object o1, Object o2) {
long val1 = ((Date)o1).getTime();
long val2 = ((Date)o2).getTime();
return (val1<val2 ? -1 : (val1==val2 ? 0 : 1));
}
};
}
}
