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Sorting a list of objects based on different data items in java


I have this class:

public class Friend {

private String name;
private String location;
private String temp;
private String humidity;

public String getTemp() {
    return temp;
}

public void setTemp(String temp) {
    this.temp = temp;
}

public String getHumidity() {
    return humidity;
}

public void setHumidity(String humidity) {
    this.humidity = humidity;
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}


public String getLocation() {
    return location;
}

public void setLocation(String location) {
    this.location = location;
}
}

I want to sort the list based on name, location, temperature and humidity based on user input.
EDIT: The user indicates which data member should sort.
What is the easiest way to do this?
Thank.

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3 answers

Java has a static function called Collections.sort(List, Comparator)that sorts a (generic) list of objects with a given custom comparator, which, given two objects of the same type, determines which one is ordered before the other.

- , Comparator, . :

public Comparator<Friend> getComparator(final String sortBy) {
  if ("name".equals(sortBy)) {
    return new Comparator<Friend>() {
      @Override int compare(Friend f1, Friend f2) 
        return f1.getName().compareTo(f2.getName());
      }
    };
  } else if ("location".equals(sortBy)) {
    return new Comparator<Friend>() {
      @Override int compare(Friend f1, Friend f2) 
        return f1.getLocation().compareTo(f2.getLocation());
      }
    };
  } else if ("temp".equals(sortBy)) {
    // ...
  } else {
    throw new IllegalArgumentException("invalid sort field '" + sortBy + "'");
  }
}
+5

, Comparable . , sort-by. Comparable sort-by, name. - .

public class FriendNameComparator extends Comparator<Friend> {

    // assuming both are non-null for code simplicity; you may wish to change that
    public int compare(Friend f1, Friend f2) {
        return f1.getName().compareTo(f2.getName());
    }
}

public class FriendLocationComparator extends Comparator<Friend> {

    // assuming both are non-null for code simplicity; you may wish to change that
    public int compare(Friend f1, Friend f2) {
        return f1.getLocation().compareTo(f2.getLocation());
    }
}

// and so forth

Collections .

Collections.sort(friendsList, new FriendNameComparator()); // sorts by name
Collections.sort(friendsList, new FriendLocationComparator()); // sorts by location
// etc
+5
List list=new ArrayList();

else, :

if(location ){
        Collections.sort(list, new Comparator () {
             public int compare(YourObject o1, YourObject o2) {
                    return o1.getLocation().compareTo(o2.getLocation());
                }

        });

    }

    } else if(temp ){

    ........
    }
    .......
+1

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