Fall Semester 2009

Here's a simplification of it (note the use of java.util.Arrays.toString()).

Also, here's how you print formatted output:

import java.util.*;

class One {
  public static void main(String[] args) {
    int[][] m = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};
    System.out.println(Arrays.deepToString(m));
    for (int i = 0; i < m.length; i++) {
      for (int j = 0; j < m[i].length; j++) 
        System.out.printf("%4d ", m[i][j]);
      System.out.println(); 
    }
  } 
}

Code for a problem and its solution below:

import java.util.*;

class Student implements Comparable {
  double gpa; 
  Student(double gpa) {
    this.gpa = gpa; 
  } 
  public String toString() {
    return "S(" + this.gpa + ")"; 
  } 
  public int compareTo(Student other) { 
    if (this.gpa - other.gpa > 0) return 1; 
    else if (this.gpa - other.gpa < 0) return -1;
    else return 0; 
    // return (int) (this.gpa - other.gpa); does not work well!
    // 3.9 - 3.1 = 0.8 truncates to 0 instead of 1 and so on...
  } 
}

class One {
  public static void main(String[] args) {
    ArrayList students = new ArrayList();
    students.add(new Student(2.1)); 
    students.add(new Student(3.9)); 
    students.add(new Student(2.5)); 
    students.add(new Student(1.1)); 
    students.add(new Student(3.1)); 
    students.add(new Student(1.9)); 
    students.add(new Student(0.3)); 
    System.out.println( students );

    Collections.sort( students );

    System.out.println( students );    

  }
}