Hierarchy
package: java.lang.Comparable
Definition
Sorting interface that designed for a condition by overriding compareTo method. For example, you can sort list in ascending order of size.
about the compareTo() method
if compareTo() method return positive number, swap the input parameters
else will be remain same
| condition | return |
|---|---|
| First parameter < second parameter | negative |
| First parameter == second parameter | 0 |
| First parameter > second parameter | positive |
How to use
customObject implements Comparable<>
Arrays.sort(customObject);
Collections.sort(customObject);
Example
import java.lang.Comparable;
public class customPoint implements Comparable<customPoint> {
private int x = 0;
private int y = 0;
public customPoint(int x, int y) {
this.x = x;
this.y = y;
}
public int getX() {
return x;
}
public int getY() {
return y;
}
@Override
public int compareTo(customPoint p2) {
if (this.y > p2.y) {
return 1; // y is in ascending order
}
return -1;
}
}
import java.util.List;
import java.util.ArrayList;
import java.util.Collections;
public class Main {
public static void main(String[] args) {
List<customPoint> pointList2 = new ArrayList<>();
pointList2.add(new customPoint(10, 10));
pointList2.add(new customPoint(1, 8));
pointList2.add(new customPoint(5, 2));
pointList2.add(new customPoint(1, 2));
pointList2.add(new customPoint(5, 5));
pointList2.add(new customPoint(10, 1));
System.out.println("current list");
for (customPoint temp : pointList2) {
System.out.println("x: " + temp.getX() + " " + "y: " + temp.getY());
}
System.out.println("sorted list");
Collections.sort(pointList2);
for (customPoint temp : pointList2) {
System.out.println("x: " + temp.getX() + " " + "y: " + temp.getY());
}
}
}
Result
current list
x: 10 y: 10
x: 1 y: 8
x: 5 y: 2
x: 1 y: 2
x: 5 y: 5
x: 10 y: 1
sorted list
x: 10 y: 1
x: 1 y: 2
x: 5 y: 2
x: 5 y: 5
x: 1 y: 8
x: 10 y: 10