mcmlength.java

JAVA 2 入门经典 的 书上代码

//CHAPTER 5, SOLUTION 4
/*
   The only change to the class definition is the addition of the package statement.
   To compile the package, the current directory should be directory containing 
   the Measures directory and the command should be:
   
   javac -source 1.4 Measures/mcmLength 

*/
package Measures;      

public class mcmLength {

  public static final int CM_PER_M = 100;
  public static final int MM_PER_CM = 10;
  public static final int MM_PER_M = MM_PER_CM*CM_PER_M;

  // Private member variables:
  private int meters = 0;
  private int centimeters = 0;
  private int millimeters = 0;

  // Constructors:
  public mcmLength(double cm) {
    this((int)Math.round(cm*MM_PER_CM));
  }

  public mcmLength(int mm) {

    meters = mm/MM_PER_M;
    centimeters = (mm - meters*MM_PER_M)/MM_PER_CM;
    millimeters = mm - meters*MM_PER_M - centimeters*MM_PER_CM;
  }

  // If we were to just store the argument values, we could
  // end up with invalid mm and cm values in the object if the
  // values passed as arguments are not valid. 
  // With the approach here we guarantee all values are valid
  // in the object that is created.
  public mcmLength(int m, int cm, int mm) {
    this(m*MM_PER_M + cm*MM_PER_CM + mm);
  }

  public mcmLength(){}

  // Methods
  public String toString() {     // Replaces the default toString method in Object:
    return Integer.toString(meters) + "m " + centimeters + "cm " + millimeters + "mm";
  }

  public int toMM() {
    return meters*MM_PER_M + centimeters*MM_PER_CM + millimeters;
  }


  public double toMeters() {
    return meters + ((double)(centimeters))/CM_PER_M + ((double)(millimeters))/MM_PER_M;
  }

  // All of the following methods use the toMM():
  public mcmLength add(mcmLength length)
  {
    return new mcmLength(toMM()+length.toMM());
  }

  public mcmLength subtract(mcmLength length)
  {
    return new mcmLength(toMM()-length.toMM());
  }

  public mcmLength multiply(int n)
  {
    return new mcmLength(n*toMM());
  }

  public mcmLength divide(int y)
  {
    return new mcmLength(toMM()/y);
  }

  //Calculate area in square mm
  public long area(mcmLength length) {	
    return (toMM()*length.toMM());
  }

  // Compare two lengths 
  // Return value is 1 if current greater than arg
  //                 0 if current equal to arg
  //                -1 if current less than arg

  public int compare(mcmLength length) {
    return greaterThan(length) ? 1 : (equals(length) ? 0 : -1);
  }

  public boolean equals(mcmLength length) {
  	return toMM() == length.toMM();
  }

  public boolean lessThan(mcmLength length) {
  	return toMM() < length.toMM();
  }

  public boolean greaterThan(mcmLength length) {
  	return toMM() > length.toMM();
  }
}