Got probably a simple problem but where ever I google it it seems the problem
is a semicolon at the end of the if statement, the problem is eclipse giving me the syntax error asking to delete my else on the else if statement, this happens nearly all the time for me and i end up using multiple IF's.
if(saleStatus == false || offerPrice <= currentOffer)
{
System.out.print("Error, sale is not open");
return false;
}
else if(currentOffer >= reservePrice)
{
saleStatus = false;
}
Every path your function can take must return a value, if you specify that it will return something.
In this case, you have probably specified it as
access_modifier boolean function_name(params){
... // ^return type
}
So, all code paths must return a boolean.
In your code, if it takes the else... path, and exits without returning anything, that isn't permitted.
else if(currentOffer >= reservePrice)
{
saleStatus = false;
//return something here (null if you don't care)
}
//or return something here (which all code-paths hit)
If you use an IDE like Eclipse, it can warn you in advance about things like this.
There's no return statement in your else block. If a return type is declared in your method, the method would not know what to return if the code enters the else block.
Put one in it or after (*).
In the first if, you return a value, so there is no point on specifying "else" because the rest of the method is not executed.
Some developers avoid multiple return statements in functions for code quality.
I wrapped your code in a class declaration, with minimum additional declarations, and a return after the whole if-else structure, and Eclipse shows no errors. I suggest writing a similarly minimal complete program that does show the problem, and posting it.
You do not need "else if" rather than "if" for the second test, but it should be harmless.
public class Bad {
boolean saleStatus;
int offerPrice;
int currentOffer;
int reservePrice;
public boolean problem() {
if(saleStatus == false || offerPrice <= currentOffer)
{
System.out.print("Error, sale is not open");
return false;
}
else if(currentOffer >= reservePrice)
{
saleStatus = false;
}
return true;
}
}
Related
To summarize I am making a program for a metro ticket system. and I am using set and get methods for it, when it comes to boolean values (since I need to validate that the person enters enough money for the ticket) how am i supposed to put in the main class( it is defined in brain) using the set method and an if statement.Here is a little fraction of the entire code and the rest is on github(https://github.com/alexxei4/subwayticket). The main is basically the class that will be used for interaction with the user and the brain is where alot of the actions are defined.All help is appreciated, please and thank you.
if (Choice1a == 10){
if(subway1.ticketcounter1(true);){
System.out.println("PRINT SUCCESSFUL, COLLECT YOUR TICKET!");
}
if(subway1.ticketcounter1(false);){
System.out.println("INSEFFICIENT FUNDS, PLEASE ADD MORE");
}
This is not how you evaluate boolean values, you just place the value in an if statement and it will proceed if true and refuse if false, also there is no need to duplicate the statement when you can just place an else block to handle situations that are not true:
if(subway1.ticketcounter1) {
System.out.println("PRINT SUCCESSFUL, COLLECT YOUR TICKET!");
}
else {
System.out.println("INSEFFICIENT FUNDS, PLEASE ADD MORE");
}
Also do not include semicolons in if statements, that's incorrect syntax. Read more about how to use use boolean values here: https://codingbat.com/doc/java-if-boolean-logic.html
EDIT:
After reading through your Github code I see that ticketcounter1 indeed is a method, but what it's doing is trying to change the value of ticketcounter1 like it's a referenced object, but boolean are primitive data types and can't be referenced, and even if they could it still wouldn't work because Java is a pass-by-value language. Read here for more information on that.
public void ticketcounter1(boolean ticketcounter1){
if (credit1 > total1){
ticketcounter1 = true;
}
else {
ticketcounter1 = false;
}
}
public void ticketcounter2(boolean ticketcounter2){
if (credit2 > total2){
ticketcounter2 = true;
}
else {
ticketcounter2= false;
}
Like the other answer said you should be returning the value as boolean instead of trying to change it:
public boolean ticketcounter1(){
if (credit1 > total1){
return true;
}
else {
return false;
}
}
public boolean ticketcounter2(){
if (credit2 > total2){
return true;
}
else {
return false;
}
}
But all in all your code demonstrated fundamental flaws in understanding how the language works, I would suggest picking up a good Java for beginners kind of book or do some introductory online tutorials. Here is a good place to start your learning journey: https://docs.oracle.com/javase/tutorial/java/index.html
You code is like this
public void ticketcounter1(boolean ticketcounter1){
if (credit1 > total1){
ticketcounter1 = true;
}
else {
ticketcounter1 = false;
}
}
public void ticketcounter2(boolean ticketcounter2) {
if (credit2 > total2){
ticketcounter2 = true;
}
else {
ticketcounter2= false;
}
}
It should be like this. Instead of using the variable and passing it though parameter. Use getter. Besides that your code won't run since subway1.ticketcounter1(true) is giving nothing. It is only changing variables stored in Brain.java. No information is being sent to main.
public boolean ticketcounter1(){
if (credit1 > total1){
return true;
}
else {
return false;
}
}
public boolean ticketcounter2(){
if (credit2 > total2){
return true;
}
else {
return false;
}
}
You can create functions without parameters. I don't know what were you trying to do?
if (Choice1a == 10){
if(subway1.ticketcounter1()){
System.out.println("PRINT SUCCESSFUL, COLLECT YOUR TICKET!");
}
if(subway1.ticketcounter1()){
System.out.println("INSEFFICIENT FUNDS, PLEASE ADD MORE");
}
}
subway1.ticketcounter1() will give either true and false. Do not use ; in if statement condition. ; ends the statement. Check this guide to learn about use of semi-colon If you do want to use ; The code should look like this
if (Choice1a == 10){
boolean ticketCounter1 = subway1.ticketcounter1();
if(ticketCounter1){
System.out.println("PRINT SUCCESSFUL, COLLECT YOUR TICKET!");
} else {
System.out.println("INSEFFICIENT FUNDS, PLEASE ADD MORE");
}
}
P.S You don't need two ifs if-else would be better in this case
if(condition) {
// Conditions is true
} else {
// Condition is false
}
I'm working on a basic Java assignment for school. This snippet involves searching for a specific part number in an ArrayList. When I try to compile, the IDE says I have a missing return statement. However, I can't see where it is. Do I need a return statement following the increment of the index? If so, then the return null becomes unreachable. Thank you guys very much.
public InventoryItem findInventoryItem(int searchPartNumber)
{
int index = 0;
boolean searching = true;
while (index < items.size() && searching){
InventoryItem inventoryItem = items.get(index);
int fetchedPartNumber = inventoryItem.getPartNumber();
if(fetchedPartNumber == (searchPartNumber)){
searching = false;
return inventoryItem;
}
else{
index++;
}
if(searching){
return null;
}
}
}
your code has several problems:
after you compared first item in list and it does not match - you will stop comparing, as searching is true and you will return null
in case of empty list you need to return null too
here is the fixed version:
public InventoryItem findInventoryItem(int searchPartNumber) {
for (InventoryItem inventoryItem : items)
if (inventoryItem.getPartNumber() == searchPartNumber)
return inventoryItem;
return null;
}
The method expected a return value in all cases. This means you have to add a return value in the else-block, too. Or you could add a return value only once at the end of all statements.
you're not handling the case where search will not be true.
That is,
if(searching){
return null;
}
Where is the else part handled here?
No matter what happens in your method, there has to be some value returned (even if it is null).
Right now, if you never get into your while (because that condition isn't fulfilled to begin with -> like when items.size() is 0), your method won't return anything.
In other words: Put a return null; after the closing bracket of your while loop.
Another important note: You do realize that this while will always only look at the first item, right? Because if your first item is not the one you're searching for, your variable searching will still be true, which will then force the method to return null (without looking at any other items)
You are missing a return statement right at the end, after the while loop.
This is needed to handle the case where the while loop guard becomes false, either by items being empty, or searching being set to false.
The compiler has no way of determining whether these will never become false, so you it requires you to return in case they do.
All functions that have a type (aren't void) require that you return something based on the method signature. This means that you must return something in ALL cases. You haven't included the case where searching is not true, and must return something if that is the case.
if(searching){
return null;
} else{
//return something else
}
It is important to note though that in this case the else is implicit, and therefore you don't actually have to provide the else. You could instead just do this:
if(searching){
return null;
}
//return something else
Keep in mind that if searching is true, it will return null and "return something else" will never be called.
Do like this
public InventoryItem findInventoryItem(int searchPartNumber)
{
int index = 0;
//boolean searching = true; comment out this line
InventoryItem inventoryItem = null; //declare null InventoryItem here
while (index < items.size())
{
inventoryItem = items.get(index);
int fetchedPartNumber = inventoryItem.getPartNumber();
if (fetchedPartNumber == (searchPartNumber))
{
//searching = false; comment out this line
break; //do something to get out from while loop
}
else {
inventoryItem = null;
index++;
}
}
return inventoryItem; //if found then it will have item otherwise null
}
First you need to return if items.size equals zero. Second you need to return if you find nothing. Third I can't see any usefulness of the variable searching.
You could change your searching function a bit. The final form would be something like this:
public InventoryItem findInventoryItem(int searchPartNumber) {
int index = 0;
while (index < items.size()){
InventoryItem inventoryItem = items.get(index);
int fetchedPartNumber = inventoryItem.getPartNumber();
if(fetchedPartNumber == searchPartNumber)
return inventoryItem;
else
index++;
}
return null;
}
This is my first time asking a question here, so I'll ask you to bear with me: I am trying to create a public boolean method, isEven(), that will check if a number is evenly divisible by two and return a value of true or false based on that. However, as this is a public method, I am unsure of how exactly to write it; this is my process thus far:
public boolean isEven()
{
if(WHAT_GOES_HERE? % 2 == 0)
return true;
else
return false;
}
I would appreciate some advice on how exactly to go about writing this method; thanks in advance!
The simplest way would be
public boolean isEven(int value){
return value % 2 == 0;
}
Using an if/else statement to return or set variables to boolean values is almost always redundant. Since you can return the condition you put in the if/else itself, the if/else is not needed.
Can anyone see why I would receive the error "This method must return a result of type Card", when I clearly returns that variable "card" which is of type Card?
public Card playCard(int id){
int i = 0;
for (Card element : hand){
if (i <= hand.size())
{
if (element.getID() == id)
{
Card card = hand.get(i);
hand.remove(i);
return card;
}
else
{
i++;
}
}
else
{
throw new NullPointerException("Card does not exist in hand");
}
}
}
Your method doesn't return anything except in one possible scenario. It has to return something (or throw an exception) in all possible scenarios.
I think you meant to do this:
public Card playCard(int id){
for (Card element : hand) {
if (element.getID() == id) {
return element;
}
}
throw new SomeAppropriateException("Card does not exist in hand");
}
...but I'm guessing a bit (as I don't know what hand is, but it looked a lot like a List). That code will always either execute the return statement or throw an exception, there's no way to get to the end of the method without one of those things happening.
Note that throwing a NullPointerException for a condition that isn't caused by a null pointer is a Bad Idea(tm). (It's also best to be consistent in where you put your { and }.)
As hinted at by Tarlen, your code would need to be modified as such:
public Card playCard(int id){
int i = 0;
for (Card element : hand){
if (i <= hand.size())
{
if (element.getID() == id)
{
Card card = hand.get(i);
hand.remove(i);
return card;
}
else
{
i++;
}
}
else
{
throw new NullPointerException("Card does not exist in hand");
}
}
return null;
}
I believe that will account for all of the possible routes your program will need to take. You always gotta keep track of returning something EVERYWHERE the method can exit. If it can exit without hitting a return statement, you'll see that error.
Your method signature is:
public Card playCard(int id){
which means you must return a Card object. Your code only has one return statement, but there are many paths through the code. You must return a Card object for each path
It is because if hand is empty, then no value is being returned.
Add a return or a throw after your for loop.
You need to have a default return statement (or exception/error) for the whole method or at least one return statement (or exception/error) for every possible execution path in your code. As it is right now you have neither of them.
I have written this function which will set
val=max or min (if val comes null)
or val=val (val comes as an Integer or "max" or "min")
while calling i am probably sending checkValue(val,"min") or checkValue(val,"max")
public String checkValue(String val,String valType)
{
System.out.println("outside if val="+val);
if(!val.equals("min") && !val.equals("max"))
{
System.out.println("Inside if val="+val);
try{
System.out.println("*Inside try val="+val);
Integer.parseInt(val);
}
catch(NumberFormatException nFE)
{
System.out.println("***In catch val="+val);
val=valType;
}
return val;
}
else
{
return val;
}
}
But the problem is if val comes null then
outside if******val=null
is shown.
Can any1 tell me is this a logical mistake?
And why will I correct?
If val is null, then the expression val.equals("min") will throw an exception.
You could correct this by using:
if (!"min".equals(val) && !"max".equals(val))
to let it go inside the if block... but I would personally handle it at the start of the method:
if (val == null) {
// Do whatever you want
}
Btw, for the sake of readability you might want to consider allowing a little more whitespace in your code... at the moment it's very dense, which makes it harder to read.
...the problem is if val comes null then outside if****val=null is shown. Can any1 tell me is this a logical mistake?
The output is correct; whether you want it to come out that way is up to you.
Your next line
if(!val.equals("min") && !val.equals("max")){
...will throw a NullPointerException because you're trying to dereference val, which is null. You'll want to add an explicit check for whether val is null:
if (val == null) {
// Do what you want to do when val == null
}
you should use valType instead of val to check either minimum or maximum is necessary to check.
My advice to you in such cases to use boolean value or enum instead of strings. Consider something like that:
/**
* check the value for minimum if min is true and for maximum otherwise
*/
public String checkValue(String val, boolean min){
if (min) {
// ...
} else {
// ...
}
}
If you need to compare strings against constants you should write it the other way around to make it null-safe:
if (! "min".equals(val))
And while this is mostly a style issue, I would make all method arguments final and not re-assign them (because that is confusing), and you can also return from within the method, not just at the end. Or if you want to return at the end, do it at the very end, not have the same return statement in both the if and the else branch.