Develop Reference

Is it possible to shorten this code?

I'm not exactly a beginner in Java, but I'm also not an expert. Is there any way to shorten this code so that it takes up less space and possibly fewer lines?
JOptionPane.showMessageDialog(null, "The student's names are: "
+ roster[0][0] + " " + roster[1][0] + ", "
+ roster[0][1] + " " + roster[1][1] + ", "
+ roster[0][2] + " " + roster[1][2] + ", and "
+ roster[0][3] + " " + roster[1][3] + ".");

Let's refactoring the code step by step
introduce variables to remove duplication.
T[] col1 = roster[0];
T[] col2 = roster[1];
String content = col1[0] + " " + col2[0] + ", "
+ col1[1] + " " + col2[1] + ", "
+ col1[2] + " " + col2[2] + ", and "
+ col1[3] + " " + col2[3] + ".";
JOptionPane.showMessageDialog(null,"The student's names are: " + content);
separate string concatenation into multi-assignments, then all assignments are the same except the last one.
int i = 0;
String content = "";
content += col1[i] + " " + col2[i] + ", ";i++;
content += col1[i] + " " + col2[i] + ", ";i++;
content += col1[i] + " " + col2[i] + ", ";i++;
content += "and " + col1[i] + " " + col2[i] + ".";i++;
make the multi-assignments consistent by using ternary operator.
int i = 0;
String content = "";
content+= (i==3?"and ":"") + col1[i]+" "+col2[i] + (i==3?".":", "); i++;
content+= (i==3?"and ":"") + col1[i]+" "+col2[i] + (i==3?".":", "); i++;
content+= (i==3?"and ":"") + col1[i]+" "+col2[i] + (i==3?".":", "); i++;
content+= (i==3?"and ":"") + col1[i]+" "+col2[i] + (i==3?".":", "); i++;
using while-loop to remove duplication.
int i = 0;
String content = "";
while(i<=3) {
content+= (i==3?"and ":"") + col1[i]+" "+col2[i] + (i==3?".":", ");
i++;
}
replacing while-loop with for-loop.
String content = "";
for (int i = 0; i <= 3; i++) {
content+= (i==3?"and ":"") + col1[i]+" "+col2[i] + (i==3?".":", ");
}
introduce variables to make the code more readable.
String content = "";
for (int i = 0; i <= 3; i++) {
String prefix = i == 3 ? "and " : "";
String current = col1[i] + " " + col2[i];
String suffix = i == 3 ? "." : ", ";
content += prefix + current + suffix;
}
inline the variables col1 & col2 that is used only once:
String content = "";
for (int i = 0; i <= 3; i++) {
String prefix = i == 3 ? "and " : "";
String current = roster[0][i] + " " + roster[1][i];
String suffix = i == 3 ? "." : ", ";
content += prefix + current + suffix;
}
replace magic number 3 with constant and the final code is below:
final int last = 3;
String content = "";
for (int i = 0; i <= last; i++) {
String prefix = i == last ? "and " : "";
String suffix = i == last ? "." : ", ";
String current = roster[0][i] + " " + roster[1][i];
content += prefix + current + suffix;
}
JOptionPane.showMessageDialog(null, "The student's names are: " + content);

StringBuilder message = new StringBuilder("The student's names are: ");
for (int i = 0; i < roster[0].length; i++) {
message
.append(roster[0][i])
.append(" ")
.append(roster[1][i]);
if (i < roster[0].length - 1)
message.append(", ");
if (i == roster[0].length - 2)
message.append("and ")
}
message.append(".");
JOptionPane.showMessageDialog(null, message.toString());
Possibly something like that. As you can see, you don't really save any lines, but obviously the code is more flexible as it can account for a variable length roster.

You can do the following: Initially assign the normal statement that you do not want repeated. Then loop through roster.
String rosterString= "The student's names are: ";
for(int i=0;i<= roster.length;i++){
for(int j=0;j<= roster[i].length;j++){
rosterString += (roster[i][j] + " ");
if (i == 1 && j < 2) {
rosterString += ", ";
}
else if (i == 1 && j == 2) {
rosterString += ", and";
}
else if (i == 1 && j == 3) {
rosterString += ".";
}
else {
rosterString += " ";
}
}
}
And then pass rosterString to your method.

String rosterString = "";
for(int i = 0; i < roster[0].length; i++) {
rosterString += roster[0][i] + " " + roster[1][i] + ", ";
}
That code will create a string with the names and commas. You could then add in if statements to check if it is near the end to change the , to an and or .

Writing to file from an array

I've been trying to write a method in java to write data from an array to a text file but I'm getting two errors.
public void WriteStudentDetailsToFile() {
PrintWriter out = null;
try {
out = new PrintWriter("StudentDetails.txt");
} catch (FileNotFoundException ex) {
System.out.println(ex.getMessage());
System.out.println("in " + System.getProperty("user.dir"));
System.exit(1);
}
for (int i = 0; i < enrolment.length; i += 1) {
if (enrolment[i] != null) {
Student a = this.enrolment[i];
if (a.getName().equals("") || a.getAddress().equals("") || a.getDOB().equals("") || a.getGender().equals("")) {
break;
} else {
String record = a.getName() + "\t" + "0" + "\t" + a.getAddress() + "\t" a.getDOB() + "\t" + a.getGender();
out.println(record);
}
}
}
}
}
The two errors are
C:\Users\B00661059\Downloads\Assignment 2\Assignment 2\Student_Enrolment.java:137: error: ';' expected
String record = a.getName() + "\t" + "0" + "\t" + a.getAddress() + "\t" a.getDOB() + "\t" + a.getGender();
^
C:\Users\B00661059\Downloads\Assignment 2\Assignment 2\Student_Enrolment.java:137: error: not a statement
String record = a.getName() + "\t" + "0" + "\t" + a.getAddress() + "\t" a.getDOB() + "\t" + a.getGender();

On line 137, you need to add a concatenation operator (+) here:
"\t" + a.getDOB()

The most obvious error is that you are missing a plus here: + "\t" a.getDOB() +.
It should be
String record = a.getName() + "\t" + "0" + "\t" + a.getAddress() + "\t" + a.getDOB() + "\t" + a.getGender();
You might also want to look into how to define and use a toString() function in your Student class to control the string representation of the object.

Try this :
String record = a.getName() + "\t" + "0" + "\t" + a.getAddress() + "\t" + a.getDOB() + "\t" + a.getGender();
instead of this :
String record = a.getName() + "\t" + "0" + "\t" + a.getAddress() + "\t" a.getDOB() + "\t" + a.getGender();
Also this doesn't make sense :
if (a.getName().equals("") || a.getAddress().equals("") || a.getDOB().equals("") || a.getGender().equals("")) {
break;
}
Since you are only interested in the else branch you can negate it.
if !(a.getName().equals("") || a.getAddress().equals("") || a.getDOB().equals("") || a.getGender().equals("")) {
// Do what you want
}

Removing all occurrences of a key only removes one

I have the following:
ArrayList<GregorianCalendar> toRemove = new ArrayList<GregorianCalendar>();
SortedSet<GregorianCalendar> copyKeys = new TreeSet<GregorianCalendar>(MyCalendarTester.myCal.getMyCalHash().keySet());
for(GregorianCalendar remove: toRemove){
copyKeys.removeAll(Collections.singleton(remove));
}
And I am trying to remove every occurrence of the key "remove" in my TreeSet copyKeys. But it only seems to remove one of them. Could someone please tell me what I'm doing wrong? Please let me know if you need more information.
EDIT:
For the sake of it, here is my entire mess of a method (I know it has a few more issues that just the question that I am asking), but here is goes:
public void eventList(){
int year = -1;
GregorianCalendar tempKey = null;
ArrayList<Event> tempArr = new ArrayList<Event>();
ArrayList<GregorianCalendar> toRemove = new ArrayList<GregorianCalendar>();
int countEnd = 0;
if(MyCalendarTester.myCal.getMyCalHash().equals(null)){
System.out.println("Your calendar is empty!");
}
else{
System.out.println("Here are your events: ");
SortedSet<GregorianCalendar> keys = new TreeSet<GregorianCalendar>(MyCalendarTester.myCal.getMyCalHash().keySet());
SortedSet<GregorianCalendar> copyKeys = new TreeSet<GregorianCalendar>(MyCalendarTester.myCal.getMyCalHash().keySet());
tempKey = keys.first();
int countTotal = keys.size();
for(GregorianCalendar key : copyKeys){
GregorianCalendar copyKey = key;
Event value = MyCalendarTester.myCal.getMyCalHash().get(key);
// System.out.println(" key.get(Calendar.MONTH) = " + key.get(Calendar.MONTH));
// System.out.println("(tempKey.get(Calendar.MONTH)) = " + (tempKey.get(Calendar.MONTH)));
// System.out.println(" key.get(Calendar.DATE) = " + key.get(Calendar.DATE));
// System.out.println(" tempKey.get(Calendar.DATE) = " + (tempKey.get(Calendar.DATE)));
tempArr.add(value);
countEnd++;
if(key.get(Calendar.MONTH) == (tempKey.get(Calendar.MONTH))
&& key.get(Calendar.DATE) == (tempKey.get(Calendar.DATE))
&& key.get(Calendar.YEAR) == tempKey.get(Calendar.YEAR)){
// tempArr.add(value);
if(key.get(Calendar.YEAR) != year){
System.out.println(key.get(Calendar.YEAR));
year = key.get(Calendar.YEAR);
System.out.println(MyCalendarTester.arrayOfDays[key.get(Calendar.DAY_OF_WEEK) - 1] + ", " + MyCalendarTester.arrayOfMonths[key.get(Calendar.MONTH) - 1] + " "
+ key.get(Calendar.DATE) + " ");
}
toRemove.add(copyKey);
// toRemove.add(copyKey);
//keys.remove(copyKey);
}else{
//if(count <= 1){
//if(tempArr.size() == 1){
if(countEnd == countTotal){
tempArr.remove(tempArr.size() - 1);
}else{
if(tempArr.size() > 1){
tempArr.remove(tempArr.size() - 2);
}else{
tempArr.remove(tempArr.size() - 1);
}
if(toRemove.size() > 0){
toRemove.remove(toRemove.size() - 1);
}
}
// }
// else{
// tempArr.remove(tempArr.size() - 2);
// toRemove.remove(toRemove.size() - 1);
// }
//
// count = 0; //reset matches
//}
}
tempKey = key;
}
Collections.sort(tempArr);
for(Event e: tempArr){
if(e.endTime != null){
System.out.println(" " + e.eventName + " " + e.startTime.get(Calendar.HOUR_OF_DAY) + ":" +
e.startTime.get(Calendar.MINUTE) + " " + e.endTime.get(Calendar.HOUR_OF_DAY)
+ ":" + e.endTime.get(Calendar.MINUTE));
//tempKey = key;
// year = key.get(Calendar.YEAR);
//keys.remove(key);
}
else{
System.out.println(" " + e.eventName + " " + e.startTime.get(Calendar.HOUR_OF_DAY) + ":" +
e.startTime.get(Calendar.MINUTE));
// tempKey = key;
// year = key.get(Calendar.YEAR);
//keys.remove(key);
}
}
tempArr.clear();
//break;
for(GregorianCalendar remove: toRemove){
copyKeys.removeAll(Collections.singleton(remove));
}
for(GregorianCalendar key : copyKeys){
Event value = MyCalendarTester.myCal.getMyCalHash().get(key);
if(tempArr.size() == 0){
if(value.endTime != null){
if(key.get(Calendar.YEAR) == year){
System.out.println(MyCalendarTester.arrayOfDays[key.get(Calendar.DAY_OF_WEEK) - 1] + ", " + MyCalendarTester.arrayOfMonths[key.get(Calendar.MONTH) - 1] + " "
+ key.get(Calendar.DATE) + " " + value.startTime.get(Calendar.HOUR_OF_DAY) + ":" + value.startTime.get(Calendar.MINUTE) + " - " + value.endTime.get(Calendar.HOUR_OF_DAY)
+ ":" + value.endTime.get(Calendar.MINUTE) + " " + value.eventName);
// tempKey = key;
}else{
System.out.println(key.get(Calendar.YEAR));
System.out.println(MyCalendarTester.arrayOfDays[key.get(Calendar.DAY_OF_WEEK) - 1] + ", " + MyCalendarTester.arrayOfMonths[key.get(Calendar.MONTH) - 1] + " "
+ key.get(Calendar.DATE) + " " + value.startTime.get(Calendar.HOUR_OF_DAY) + ":" + value.startTime.get(Calendar.MINUTE) + " - " + value.endTime.get(Calendar.HOUR_OF_DAY)
+ ":" + value.endTime.get(Calendar.MINUTE) + " " + value.eventName );
year = key.get(Calendar.YEAR);
tempKey = key;
}
}else{
if(key.get(Calendar.YEAR) == year){
System.out.println(MyCalendarTester.arrayOfDays[key.get(Calendar.DAY_OF_WEEK) - 1] + ", " + MyCalendarTester.arrayOfMonths[key.get(Calendar.MONTH) - 1] + " "
+ key.get(Calendar.DATE) + " " + value.startTime.get(Calendar.HOUR_OF_DAY) + ":" + value.startTime.get(Calendar.MINUTE) + " " + value.eventName);
tempKey = key;
}else{
System.out.println(key.get(Calendar.YEAR));
System.out.println(MyCalendarTester.arrayOfDays[key.get(Calendar.DAY_OF_WEEK) - 1] + ", " + MyCalendarTester.arrayOfMonths[key.get(Calendar.MONTH) - 1] + " "
+ key.get(Calendar.DATE) + " " + value.startTime.get(Calendar.HOUR_OF_DAY) + ":" + value.startTime.get(Calendar.MINUTE) + " " + value.eventName);
System.out.println();
year = key.get(Calendar.YEAR);
tempKey = key;
}
}
}
}
}
}
I originally have it sorted by the keys (dates) in ascending order. From there, I am looking for any identical dates and sorting them by the time (values). Then, since I've already sorted and printed those days by the time, I don't want to reprint them later. I've been tweaking this for hours to try to get it to cooperate, so perhaps I'm over thinking it at this point. Anyway, if anyone is nice enough to look at this and make a few suggestions, I'd greatly appreciate it. Otherwise, just skip over because this is a long and convoluted one.

There will only be one occurrence of any given object in a Set and that is why only one is being removed.
Sets do not allow duplicates. If you want to allow duplicates, use another data structure such as an ArrayList.

Is there any possibility to get the currentStockLevel from this method?

I need the currentStockLevel for another void Method in java, is there any possibility to get it?
I think no, because of void right?
public void receive (int currentStock)
{
String outLine;
if (currentStockLevel > 0)
outLine = productCode;
{
outLine = ". Current Stock: " + currentStockLevel;
outLine += " Current Stock changed from " + currentStockLevel;
currentStockLevel += currentStock;
outLine += " to " + currentStockLevel;
int storeCost = wholeSalePrice * currentStockLevel;
System.out.println (productCode + ":" + " Received " + currentStockLevel + "." + " Store Cost " + "$" + storeCost + "." + " New stock level: " + currentStockLevel);
}

Storing part of method as another method?

Basically, I have code that uses the same few lines in different scenarios, and it makes the code a bit messy (especially since I probably overcomplicated what I made, but that's another issue). What I wanted to do is store that piece of code as another function and calling it in the longer one. WHich should work as far as I know, except, the longer function has variables that aren't set in the shorter one, and if they were, I'm pretty sure it would change the final result of the function.
Here is the longer code:
public static void combat(Character a,Character b){
int battleturn = 1;
int maxTurns=20;
int draw1 = 0;
//stop after 20 turns, or stop when one player has 0 HP.
while (a.health > 0 && b.health > 0 && maxTurns > 0){
/* run a round of combat*/
if (b.health < 0.25 * b.maxHealth){
if (b.getFlee(a)){
System.out.println(">>>>>>>>>>The enemy has fled successfully<<<<<<<<<<");
break;
}else{
System.out.println("Battle turn " + battleturn + ", <attack> or <flee>?");
Scanner input = new
Scanner(System.in);
String move = input.next();
while(!move.equals("attack") && !move.equals("flee")){
System.out.println("Error: Please input <attack> or <flee>.");
input = new Scanner(System.in);
move = input.next();
}
if (move.equals("attack")){
System.out.println(a.name + " dealt " + a.combatRound(b) + " damage to " + b.name + "." + " Enemy has "
+ b.getHealth() + "/" + b.getMaxHealth() + " health.");
System.out.println(b.name + " dealt " + b.combatRound(a) + " damage to " + a.name + "." + " You have " +
a.getHealth() + "/" + a.getMaxHealth() + " health");
maxTurns--;
battleturn++;
}else if(move.equals("flee")){
if (a.getFlee(b)){
draw1++;
System.out.println(">>>>>>>>>>You have fled!<<<<<<<<<<");
break;
}else{
System.out.println(a.name + " dealt " + a.combatRound(b) + " damage to " + b.name + "." + " Enemy has " +
b.getHealth() + "/" + b.getMaxHealth() + " health.");
System.out.println(b.name + " dealt " + b.combatRound(a) + " damage to " + a.name + "." + " You have " +
a.getHealth() + "/" + a.getMaxHealth() + " health");
maxTurns--;
battleturn++;
}
}
}
}else{
System.out.println("Battle turn " + battleturn + ", <attack> or <flee>?");
Scanner input = new
Scanner(System.in);
String move = input.next();
while(!move.equals("attack") && !move.equals("flee")){
System.out.println("Error: Please input <attack> or <flee>.");
input = new Scanner(System.in);
move = input.next();
}
if (move.equals("attack")){
System.out.println(a.name + " dealt " + a.combatRound(b) + " damage to " + b.name+ "." + " Enemy has " +
b.getHealth() + "/" + b.getMaxHealth() + "health.");
System.out.println(b.name + " dealt " + b.combatRound(a) + " damage to " + a.name + "." + " You have " +
a.getHealth() + "/" + a.getMaxHealth() + " health");
maxTurns--;
battleturn++;
}else if(move.equals("flee")){
if (a.getFlee(b)){
draw1++;
System.out.println(">>>>>>>>>>You have fled!<<<<<<<<<<");
break;
}else{
System.out.println(a.name + " dealt " + a.combatRound(b) + " damage to " + b.name+ "." + " Enemy has " +
b.getHealth() + "/" + b.getMaxHealth() + " health.");
System.out.println(b.name + " dealt " + b.combatRound(a) + " damage to " + a.name + "." + " You have " +
a.getHealth() + "/" + a.getMaxHealth() + " health");
maxTurns--;
battleturn++;
}
}
}
}
}
As you can see there is a part of code that is repeated, and that is.
System.out.println("Battle turn " + battleturn + ", <attack> or <flee>?");
Scanner input = new
Scanner(System.in);
String move = input.next();
while(!move.equals("attack") && !move.equals("flee")){
System.out.println("Error: Please input <attack> or <flee>.");
input = new Scanner(System.in);
move = input.next();
}
if (move.equals("attack")){
System.out.println(a.name + " dealt " + a.combatRound(b) + " damage to " + b.name + "." + " Enemy has "
+ b.getHealth() + "/" + b.getMaxHealth() + " health.");
System.out.println(b.name + " dealt " + b.combatRound(a) + " damage to " + a.name + "." + " You have " +
a.getHealth() + "/" + a.getMaxHealth() + " health");
maxTurns--;
battleturn++;
}else if(move.equals("flee")){
if (a.getFlee(b)){
draw1++;
System.out.println(">>>>>>>>>>You have fled!<<<<<<<<<<");
break;
}else{
System.out.println(a.name + " dealt " + a.combatRound(b) + " damage to " + b.name + "." + " Enemy has " +
b.getHealth() + "/" + b.getMaxHealth() + " health.");
System.out.println(b.name + " dealt " + b.combatRound(a) + " damage to " + a.name + "." + " You have " +
a.getHealth() + "/" + a.getMaxHealth() + " health");
maxTurns--;
battleturn++;
}
}
}
It won't compile if I set that chunk of code as a method, because it doesn't have the variables battleturn, maxturns, draw1, but if I put them in there, the amount of battle turns messes up.
Any ideas?

Java applications should be modular: each class fulfilling its own function, each method generally performing a single operation.
In a method you can use either class variables or its own local variables.
If you need several methods work with the same data, it should either be part of a class (instance and/or static variables) or passed to each method as parameters.
Make sure that you do not define class variables in a method. This will create local variables that will shadow class variables.

This might help you accomplish what you're trying to do.
private static void reportDamage(Character a,
Character b) {
System.out.println(a.name + " dealt "
+ a.combatRound(b) + " damage to " + b.name
+ "." + " Enemy has " + b.getHealth() + "/"
+ b.getMaxHealth() + " health.");
}
I suggest changing your combat method like this.
int battleturn = 0;
int maxTurns = 20;
// stop after 20 turns, or stop when one player has 0
// HP.
Scanner input = new Scanner(System.in);
try {
while (a.health > 0 && b.health > 0
&& battleturn < maxturn) {
battleturn++;
/* run a round of combat */
if (b.getFlee(a)) {
System.out.println(">>>>>>>>>>"
+ "The enemy has fled successfully"
+ "<<<<<<<<<<");
break;
} else {
System.out.println("Battle turn "
+ battleturn + ", <attack> or <flee>?");
boolean isFlee = false;
boolean isAttack = false;
String move = input.next();
for (;;) {
isAttack = "attack".equalsIgnoreCase(move);
isFlee = "flee".equalsIgnoreCase(move);
if (isFlee || isAttack) {
break;
}
System.out.println("Error: "
+ "Please input <attack> or <flee>.");
move = input.next();
}
if (isAttack) {
reportDamage(a, b);
reportDamage(b, a);
} else { // isFlee
if (a.getFlee(b)) {
System.out.println(">>>>>>>>>>"
+ "You have fled successfully"
+ "<<<<<<<<<<");
break;
} else {
// b is fleeing.
// reportDamage(a, b);
reportDamage(b, a);
}
}
}
}
} finally {
input.close();
}