Hi i run into a problem when sorting an arrayList as following (and yes i have imported util):
Collections.sort(personer);
I have this list:
private List<Person> personer;
public Register() {
personer = new ArrayList<Person>();
}
But i got the error:
mittscript.java:45: cannot find symbol symbol : method sort(java.util.List) location: class java.util.Collections Collections.sort(personer);
I answered you in your other post java - alphabetical order (list)
I believe if you do it, will fix your problems.
Collection<Person> listPeople = new ArrayList<Person>();The class Person.java will implements Comparable
public class Person implements Comparable<Person>{ public int compareTo(Person person) { if(this.name != null && person.name != null){ return this.name.compareToIgnoreCase(person.name); } return 0; } }Once you have this, in the class you're adding people, when you're done adding, type:
Collections.sort(listPeople);
There're two sort methods in Collections. You can either make Person implement Comparable interface, or provide comparator as a second argument into sort.
Otherwise, there's no way for JVM to know which Person object is 'bigger' or 'smaller' than another.
So, option 1
class Person implements Comparable {
...
}
Collections.sort(list);
and option 2
Collections.sort(list, myCustomComparator);
