implementing interface
- by 1ace1
hello guys so i have this assignment that i need to implement interface to go over an ArrayList and sort it (ascending or descnding).I dont want "the" answer i just need some suggestions on my approach and why i get this error
Exception in thread "main" java.lang.ClassCastException: Week7.Check cannot be cast to java.lang.Comparable
at java.util.Arrays.mergeSort(Unknown Source)
at java.util.Arrays.sort(Unknown Source)
at java.util.Collections.sort(Unknown Source)
at Week7.TestCheck.main(TestCheck.java:18)
This is how i did it:
comparable had one method called public int compairTo(Object o)
public class Check implements comparable {
private Integer checkNumber;
public Check(Integer newCheckNumber) {
setCheckNumber(newCheckNumber);
}
public String toString() {
return getCheckNumber().toString();
}
public void setCheckNumber(Integer checkNumber) {
this.checkNumber = checkNumber;
}
public Integer getCheckNumber() {
return checkNumber;
}
@Override
public int compairTo(Object o) {
Check compair = (Check)o;
int result = 0;
if (this.getCheckNumber() > compair.getCheckNumber())
result = 1;
else if(this.getCheckNumber() < compair.getCheckNumber())
result = -1;
return result;
}
}
in my main i had this
import java.util.ArrayList;
import java.util.Collections;
public class TestCheck {
public static void main(String[] args) {
ArrayList checkList = new ArrayList();
checkList.add(new Check(445));
checkList.add(new Check(101));
checkList.add(new Check(110));
checkList.add(new Check(553));
checkList.add(new Check(123));
Collections.sort(checkList);
for (int i =0; i < checkList.size(); i++){
System.out.println(checkList.get(i));
}
}
}
