Mega Code Archive
Writing Your own Comparator
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import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
public class EmpComparator implements Comparator {
public int compare(Object obj1, Object obj2) {
Person emp1 = (Person) obj1;
Person emp2 = (Person) obj2;
int nameComp = emp1.getFirstName().compareTo(emp2.getFirstName());
return ((nameComp == 0) ? emp1.getLastName().compareTo(
emp2.getLastName()) : nameComp);
}
public static void main(String args[]) {
String names[] = { "Bart", "Hugo", "Lisa", "Marge", "Homer", "Maggie",
"Roy" };
// Convert to list
List list = new ArrayList(Arrays.asList(names));
// Ensure list sorted
Collections.sort(list);
System.out.println("Sorted list: [length: " + list.size() + "]");
System.out.println(list);
// Search for element in list
int index = Collections.binarySearch(list, "Maggie");
System.out.println("Found Maggie @ " + index);
// Search for element not in list
index = Collections.binarySearch(list, "Jimbo Jones");
System.out.println("Didn't find Jimbo Jones @ " + index);
// Insert
int newIndex = -index - 1;
list.add(newIndex, "Jimbo Jones");
System.out.println("With Jimbo Jones added: [length: " + list.size()
+ "]");
System.out.println(list);
// Min should be Bart
System.out.println(Collections.min(list));
// Max should be Roy
System.out.println(Collections.max(list));
Comparator comp = Collections.reverseOrder();
// Reversed Min should be Roy
System.out.println(Collections.min(list, comp));
// Reversed Max should be Bart
System.out.println(Collections.max(list, comp));
}
}
class Person implements Comparable {
String firstName, lastName;
public Person(String f, String l) {
this.firstName = f;
this.lastName = l;
}
public String getFirstName() {
return firstName;
}
public String getLastName() {
return lastName;
}
public String toString() {
return "[ name=" + firstName + ",name=" + lastName + "]";
}
public int compareTo(Object obj) {
Person emp = (Person) obj;
int deptComp = firstName.compareTo(emp.getFirstName());
return ((deptComp == 0) ? lastName.compareTo(emp.getLastName())
: deptComp);
}
public boolean equals(Object obj) {
if (!(obj instanceof Person)) {
return false;
}
Person emp = (Person) obj;
return firstName.equals(emp.getFirstName())
&& lastName.equals(emp.getLastName());
}
}
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