Question

Could someone please help me out with the following problem in java. I have a simple class defined as below:

public class Expr {
  public long total_apparitions;
  public String expression=new String();

  public Expr(long total,String expr){
    this.total_apparitions=total;
    this.expression=expr;
  }

  public void increment(long aparitions){
    total_apparitions+=aparitions;
  }
}

I want to sort an array of Expr objects by the total_apparitions field, using the Arrays.sort built-in function. How do I specify to the Arrays.sort function the comparison factor? Thanks a lot.

Answer 1

As @Jason Braucht said, implement Comparable like this:

public class Expr implements Comparable {
  ...
  public int compareTo(Object o) {
    if(this.total_apparitions > ((Expr) o).total_apparitions)
      return 1;
    else if(this.total_apparitions < ((Expr) o).total_apparitions)
      return -1;
    return 0;
  }
}