Contents
- ./AutoboxFixed.java
- ./Autobox.java
- ./Chicken.java
./AutoboxFixed.java 1/3
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/**
* This class demonstrates fixing the autoboxing inefficiency.
*
* @author Sara Sprenkle
*/
public class AutoboxFixed {
/**
* Called when user runs java Autobox
*/
public static void main(String[] args) {
// Find the inefficiency in the code below.
long startTime = System.currentTimeMillis();
long sum = 0L;
for (long i = 0; i < Integer.MAX_VALUE; i++) {
sum += i;
}
System.out.println(sum);
long finishTime = System.currentTimeMillis();
double seconds = (finishTime - startTime)/1000.0;
System.out.println("Elapsed time: " + seconds + " s");
}
}
./Autobox.java 2/3
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/**
* This class demonstrates inefficiencies with unnecessary autoboxing
*
* @author Sara Sprenkle
*/
public class Autobox {
public static void main(String[] args) {
// Find the inefficiency in the code below.
long startTime = System.currentTimeMillis();
Long sum = 0L;
for (long i = 0; i < Integer.MAX_VALUE; i++) {
sum += i;
}
System.out.println(sum);
long finishTime = System.currentTimeMillis();
double seconds = (finishTime - startTime)/1000.0;
System.out.println("Elapsed time: " + seconds + " s");
}
}
./Chicken.java 3/3
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import java.util.Arrays;
/**
* A simple Java class that models a Chicken. The state of the chicken is its
* name, height, weight, and gender.
*
* Made several of the accessor methods final because child classes
* shouldn't need to change them.
*
* Implements the Comparable interface--using generics, comparing
* chickens by their height.
*
* @author CSCI209
*/
public class Chicken implements Comparable<Chicken> {
// ------------ INSTANCE VARIABLES -------------------
/** the chicken's name */
private String name;
/** the height of the chicken in centimeters */
private int height;
/** the weight of the chicken in pounds */
private double weight;
/** true iff the chicken is a female */
private boolean isFemale;
/** default name for chickens */
public static String DEFAULT_NAME = "BUBBA";
/** the name of the farm the chickens are on */
public static String FARM = "McDonald";
/** the amount of weight the chicken gains during feeding */
private static double WEIGHT_GAIN = .3;
/** the amount of height the chicken gains during feeding */
private static int HEIGHT_GAIN = 1;
/** the amount of weight difference we are okay with */
public static double ERROR_TOLERANCE = .0001;
/**
* Constructs a chicken with the given characteristics.
*
* @param name the name of the chicken
* @param height the height of the chicken in centimeters
* @param weight the weight of the chicken in pounds
* @param isFemale whether the chicken is female
*/
public Chicken(String name, int height, double weight, boolean isFemale ) {
this.name = name;
this.height = height;
this.weight = weight;
this.isFemale = isFemale;
}
/**
* Constructs a chicken with the given characteristics and assumes
* the chicken is female.
*
* @param name the name of the chicken
* @param height the height of the chicken in centimeters
* @param weight the weight of the chicken in pounds
*/
public Chicken(String name, int height, double weight) {
this( name, height, weight, true );
}
/**
* Constructs a chicken with the given characteristics, assumes
* the chicken's name is Bubba (defined by DEFAULT_NAME) and that
* it is female.
* @param height the height of the chicken in centimeters
* @param weight the weight of the chicken in pounds
*/
public Chicken( int height, double weight ) {
this( DEFAULT_NAME, height, weight, true);
}
/**
* Returns a string representation of the chicken.
* Format:
* <br/>Chicken name: <name>
* <br/>weight: <weight> pounds
* <br/>height: <height> cm
* <br/>female/male
* <p>Weight is displayed to one decimal place
* @return a string representation of this Chicken
*/
@Override
public String toString() {
StringBuffer rep = new StringBuffer("Chicken name: ");
rep.append(name);
rep.append("\nweight: ");
rep.append(String.format("%.1f", weight));
rep.append(" pounds\nheight: ");
rep.append(height);
rep.append(" cm\n");
rep.append( isFemale? "female" : "male"); // Java ternary operator; also available in C
return rep.toString();
}
/**
* Determines if two Chickens are equivalent, based on their
* name, height, weight, and sex.
*/
@Override
public boolean equals(Object o) {
if( o == this ) {
return true;
}
Chicken other = (Chicken) o;
if( ! other.getName().equals(this.getName() ) ) {
return false;
}
if( other.getHeight() != this.getHeight() ) {
return false;
}
double difference = this.getWeight() - this.getWeight();
if( difference > ERROR_TOLERANCE ) {
return false;
}
if( this.isFemale() ) {
return other.isFemale();
} else {
return ! other.isFemale();
}
}
/**
* Returns a negative integer if this chicken is smaller
* in height than than the object passed as a parameter,
* returns a positive integer if this chicken is greater in height
* than the object passed as a parameter, and returns a 0 if the
* two chickens have the same height.
*/
@Override
public int compareTo(Chicken other) {
if (height < other.getHeight() )
return -1;
if (height > other.getHeight())
return 1;
return 0;
// simpler implementation : return height-other.getHeight()
}
//
// ----------- GETTER METHODS ------------
// (also Accessor methods)
/**
* Returns the height of the chicken in centimeters
*
* @return the height of the chicken, in centimeters
*/
public final int getHeight() {
return height;
}
/**
* Returns the weight of the chicken in pounds
* @return the weight of the chicken, in pounds
*/
public final double getWeight() {
return weight;
}
/**
* Returns the chicken's name
* @return the name of the chicken
*/
public final String getName() {
return name;
}
/**
* Returns whether this chicken is female.
*
* @return true if the chicken is female and false otherwise.
*/
public boolean isFemale() {
return isFemale;
}
//
// ------------- MUTATORS -----------
//
/**
* Feeds the chicken--making the chicken grow
*/
public void feed() {
weight += WEIGHT_GAIN;
height += HEIGHT_GAIN;
}
//
// ------------- SETTERS ----------
//
/**
* Sets the name of the chicken
*
* @param n
* the name of the chicken
*/
public void setName(String n) {
name = n;
}
/**
* Sets the height of the chicken
*
* @param h
* the height of the chicken, in cm
*/
public void setHeight(int h) {
height = h;
}
/**
* Sets the weight of the chicken
*
* @param w
* the weight of the chicken, in pounds
*/
public void setWeight(double w) {
weight = w;
}
/**
* @param args
* the command-line arguments
*/
public static void main(String args[]) {
int fredHeight = 38;
Chicken chicken = new Chicken("Fred", fredHeight, 2.0, false);
System.out.println(chicken);
if( chicken.getHeight() != fredHeight ) {
System.err.println("Problem likely in constructor setting height");
}
if( !chicken.getName().equals("Fred") ) {
System.err.println("Problem likely in constructor setting name");
}
chicken.feed();
int newFredHeight = chicken.getHeight();
System.out.println(chicken.getName() + " is now " + newFredHeight +
" cm tall.");
chicken.feed();
System.out.println("He's a growing boy at " + chicken.getHeight() + " cm tall and " + chicken.getWeight() + " pounds");
String expectedRep = "Chicken name: Fred\nweight: 2.6 pounds\nheight: 40 cm\nmale";
String actualRep = chicken.toString();
// Demonstrates trickiness with testing with doubles
if( ! actualRep.equals(expectedRep) ) {
System.err.println("Problem in toString");
System.err.println("\tActual: " + actualRep);
System.err.println("\tExpected: " + expectedRep);
}
Chicken trivialMatch = chicken;
if( ! chicken.equals(trivialMatch) ) {
System.err.println("Problem in equals");
System.err.println("\tActual: " + chicken.equals(trivialMatch) );
System.err.println("\tExpected: " + true);
}
Chicken grownFred = new Chicken("Fred", 40, 2.6, false);
// This doesn't work -- again issue with comparing doubles
if( ! chicken.equals(grownFred) ) {
System.err.println("Problem in equals");
System.err.println("\tActual: " + chicken.equals(grownFred) );
System.err.println("\tExpected: " + true);
}
// ---- creating tests for chickens -----
String[] names = {"Rocky", "Baby Chicken"};
double[] weights = {4.0, .8};
int[] heights = {50, 4};
Chicken[] chickens = new Chicken[3];
for( int i=0; i < names.length; i++ ) {
Chicken thisChicken = new Chicken( names[i], heights[i], weights[i] );
chickens[i] = thisChicken;
if( !thisChicken.getName().equals(names[i]) ) {
System.err.println("Problem likely in constructor setting name");
System.err.println("\tActual: " + thisChicken.getName());
System.err.println("\tExpected: " + names[i]);
}
if( thisChicken.getWeight() != weights[i] ) {
System.err.println("\tError in getWeight for Chicken " + i );
System.err.println("\tActual: " + thisChicken.getWeight());
System.err.println("\tExpected: " + weights[i] );
}
// feed the chicken and check the state
thisChicken.feed();
if( thisChicken.getWeight() != weights[i] + WEIGHT_GAIN ) {
System.err.println("Error in feed weight for Chicken " + i);
System.err.println("\tActual: " + thisChicken.getWeight());
System.err.println("\tExpected: " + (weights[i] + WEIGHT_GAIN) );
}
if( thisChicken.getHeight() != heights[i] + HEIGHT_GAIN ) {
System.err.println("Error in feed height for Chicken " + i);
System.err.println("\tActual: " + thisChicken.getHeight());
System.err.println("\tExpected: " + (heights[i] + HEIGHT_GAIN) );
}
// feed the chicken again and check the state
thisChicken.feed();
// NOTE: this test may fail, but tried to address by giving some
// error tolerance on the weight
double expectedWeight2 = weights[i] + 2 * WEIGHT_GAIN;
int comparison = Double.compare(thisChicken.getWeight(), expectedWeight2 );
if( comparison != 0 ) {
if( thisChicken.getWeight() - expectedWeight2 > ERROR_TOLERANCE ) {
System.err.println("Error in second feed weight for Chicken " + i);
System.err.println("\tActual: " + thisChicken.getWeight());
System.err.println("\tExpected: " + (expectedWeight2 ));
}
}
if( thisChicken.getHeight() != heights[i] + 2 * HEIGHT_GAIN ) {
System.err.println("Error in second feed height for Chicken " + i);
System.err.println("\tActual: " + thisChicken.getHeight());
System.err.println("\tExpected: " + (heights[i] + 2 * HEIGHT_GAIN ));
}
// TODO: test setName method
}
chickens[2] = chicken;
// sort the chickens
Arrays.sort(chickens);
// print the chickens in sorted order (by height)
for (Chicken c : chickens) {
System.out.println(c);
}
}
}
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