OnJava8-Examples/collectiontopics/ToDoList.java

// collectiontopics/ToDoList.java
// (c)2021 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
// A more complex use of PriorityQueue
import java.util.*;

class ToDoItem implements Comparable<ToDoItem> {
  private char primary;
  private int secondary;
  private String item;
  ToDoItem(String td, char pri, int sec) {
    primary = pri;
    secondary = sec;
    item = td;
  }
  @Override public int compareTo(ToDoItem arg) {
    if(primary > arg.primary)
      return +1;
    if(primary == arg.primary)
      if(secondary > arg.secondary)
        return +1;
      else if(secondary == arg.secondary)
        return 0;
    return -1;
  }
  @Override public String toString() {
    return Character.toString(primary) +
      secondary + ": " + item;
  }
}

class ToDoList {
  public static void main(String[] args) {
    PriorityQueue<ToDoItem> toDo =
      new PriorityQueue<>();
    toDo.add(new ToDoItem("Empty trash", 'C', 4));
    toDo.add(new ToDoItem("Feed dog", 'A', 2));
    toDo.add(new ToDoItem("Feed bird", 'B', 7));
    toDo.add(new ToDoItem("Mow lawn", 'C', 3));
    toDo.add(new ToDoItem("Water lawn", 'A', 1));
    toDo.add(new ToDoItem("Feed cat", 'B', 1));
    while(!toDo.isEmpty())
      System.out.println(toDo.remove());
  }
}
/* Output:
A1: Water lawn
A2: Feed dog
B1: Feed cat
B7: Feed bird
C3: Mow lawn
C4: Empty trash
*/