I'm new to java. When I compile my code on the terminal it is telling me I am getting several errors and I am not sure why. Most of the errors are "can't find symbol"
import java.util.Scanner;
public class CircularQueue {
private int head, tail;
private String [ ] q = new String [ 10 ];
private String name;
Scanner input = new Scanner (System.in);
public CircularQueue () {
head = -1;
tail = -1;
}
public void insertQueue () {
if (isQueueFull () )
System.out.println ("Overflow");
else {
name = getName ();
if (isQueueEmpty () )
head = +1;
if (tail==Size-1)
tail=-1;
q [++ tail] = name;
}
}
public void deleteQueue() {
String x;
if ( isQueueEmpty () )
System.out.println("Underflow");
else {
x=q[head];
System.out.println ("Servicing " + x);
if (head==tail) {
head=-1;
tail=-1;
}
else {
head ++;
if (head==Size)
head=0;
}
}
}
private String getName () {
System.out.println("Enter name");
return input.nextLine ();
}
public boolean isQueueEmpty () {
return (head==-1);
}
public boolean isQueueFull () {
return ((tail-head+1==0) || (tail-head+1==Size));
}
public void printQueueLogical () {
int next;
if (isQueueEmpty())
System.out.println ("Empty");
else {
next=head;
System.out.println (" q [" + next + "] = " +q[next]);
while (next != tail) {
next ++;
if (next==Size)
next=0;
System.out.println (" q [" + next + "] = " +q[next]);
}
}
}
public void printQueuePhysical () {
for (int J=0; J<Size; J++)
System.out.println (" q [" + J + "]= " + q [J]);
}
class TestCircularQueue {
public static void main ( strings [] args) {
CircularQueue n = new CircularQueue ();
for (int J=0; J<3; J++)
m.insertQueue ();
m.deleteQueue ();
m.printQueueLogical ();
}
}
}
When the compiler says it can't find a symbol, this means that you probably have a syntax error. A symbol can be a keyword, some method name, an operator, etc.
Possible causes, for example (extracted from http://java.about.com/od/cerrmsg/g/Definition-Cannot-Find-Symbol.htm)
trying to use a variable without declaring it.
misspelling a class or method name (remember, Java is case sensitive).
the parameters used do not match a method's signature.
the packaged class has not being referenced correctly using an import declaration.
What you can do?
You can read the stacktrace. The "can't find a symbol" exception usually comes with useful information, such as the offending symbol and the location in the code. For example (again, from the link above)
System.out.prontln("The perils of mistyping..");
will generate something like
cannot find symbol
symbol: method prontln(jav.lang.String)
location: class java.io.printStream
Just added some lines of code.Dint test your logic though and do not create unnecessary inner classes.
import java.util.Scanner;
public class CircularQueue {
private int head, tail;
private String [ ] q = new String [ 10 ];
private String name;
int Size;
Scanner input = new Scanner (System.in);
public CircularQueue () {
head = -1;
tail = -1;
}
public void insertQueue () {
if (isQueueFull () )
System.out.println ("Overflow");
else {
name = getName ();
if (isQueueEmpty () )
head = +1;
if (tail==Size-1)
tail=-1;
q [++ tail] = name;
}
}
public void deleteQueue() {
String x;
if ( isQueueEmpty () )
System.out.println("Underflow");
else {
x=q[head];
System.out.println ("Servicing " + x);
if (head==tail) {
head=-1;
tail=-1;
}
else {
head ++;
if (head==Size)
head=0;
}
}
}
public void setSize(int i)
{
Size=i;
}
private String getName () {
System.out.println("Enter name");
return input.nextLine ();
}
public boolean isQueueEmpty () {
return (head==-1);
}
public boolean isQueueFull () {
return ((tail-head+1==0) || (tail-head+1==Size));
}
public void printQueueLogical () {
int next;
if (isQueueEmpty())
System.out.println ("Empty");
else {
next=head;
System.out.println (" q [" + next + "] = " +q[next]);
while (next != tail) {
next ++;
if (next==Size)
next=0;
System.out.println (" q [" + next + "] = " +q[next]);
}
}
}
public void printQueuePhysical () {
for (int J=0; J<Size; J++)
System.out.println (" q [" + J + "]= " + q [J]);
}
}
class TestCircularQueue {
public static void main ( String [] args) {
CircularQueue n = new CircularQueue ();
n.setSize(10);
for (int J=0; J<3; J++)
{n.insertQueue ();
n.deleteQueue ();
n.printQueueLogical ();}
}
}
i Think "size" means the length of the Array....
ie. int size = q.length;
and for some reason when creating the object of the class you used 'n' and then when you wanted to use it you used 'm' check that also
so after going through it...i think dis worked for me..although what you are trynna achieve...but you should sort the rest yourself
import java.util.Scanner;
public class CircularQueue {
private int head, tail;
private String [ ] q = new String [ 10 ];
private String name;
int Size = q.length;
Scanner input = new Scanner (System.in);
public CircularQueue () {
head = -1;
tail = -1;
}
public void insertQueue () {
if (isQueueFull () )
System.out.println ("Overflow");
else {
name = getName ();
if (isQueueEmpty () )
head = +1;
if (tail==Size-1)
tail=-1;
q [++ tail] = name;
}
}
public void deleteQueue() {
String x;
if ( isQueueEmpty () )
System.out.println("Underflow");
else {
x=q[head];
System.out.println ("Servicing " + x);
if (head==tail) {
head=-1;
tail=-1;
}
else {
head ++;
if (head==Size)
head=0;
}
}
}
private String getName () {
System.out.println("Enter name");
return input.nextLine ();
}
public boolean isQueueEmpty () {
return (head==-1);
}
public boolean isQueueFull () {
return ((tail-head+1==0) || (tail-head+1==Size));
}
public void printQueueLogical () {
int next;
if (isQueueEmpty())
System.out.println ("Empty");
else {
next=head;
System.out.println (" q [" + next + "] = " +q[next]);
while (next != tail) {
next ++;
if (next==Size)
next=0;
System.out.println (" q [" + next + "] = " +q[next]);
}
}
}
public void printQueuePhysical () {
for (int J=0; J<Size; J++)
System.out.println (" q [" + J + "]= " + q [J]);
}
}
public class TestCircular {
/**
* #param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
CircularQueue n = new CircularQueue ();
n.insertQueue ();
n.deleteQueue ();
n.printQueueLogical ();
}
}
Related
Assuming that the array is populated with 20 shipments, calculate the total cost of local shipments in the array.
I tried to create a for loop and then call out the method calcCost() and += it to the variable local so it would save the values I guess
I'm pretty sure the way I wrote the code is wrong so if someone could help me with it that would be great!
package question;
public class TestShipment {
public static void main(String[] args) {
Shipment r1 = new Shipment(
new Parcel("scientific calculator " , 250),
new Address("Dubai","05512345678"),
new Address("Dubai","0505432123"),
"Salim"
);
System.out.println(r1);
Shipment[] arr = new Shipment[100];
arr[5] = r1;
Shipment[] a = new Shipment[20];
double local = 0;
for (int i = 0; i < a.length; i++) {
if (a[i].isLocalShipment()) {
System.out.println(a[i].calcCost());
}
}
}
}
public class Shipment {
public Parcel item;
private Address fromAddress;
private Address toAddress;
public String senderName;
public Shipment(Parcel i, Address f, Address t, String name) {
item = i;
fromAddress = f;
toAddress = t;
senderName = name;
}
//setter
public void setFromAddress(String c, String p) {
c = fromAddress.getCity();
p = fromAddress.getPhone();
}
public boolean isLocalShipment() {
boolean v = false;
if (fromAddress.getCity() == toAddress.getCity()) {
v = true;
} else {
v = false;
}
return v;
}
public double calcCost() {
double cost = 0;
if (fromAddress.getCity() == toAddress.getCity()) {
cost = 5;
} else {
cost = 15;
}
if(item.weight > 0 && item.weight <= 200) {
cost += 5.5;
}
if(item.weight > 200) {
cost += 10.5;
}
return cost = cost * (1 + 0.5); //fix the tax
}
public String toString() {
return "From: " + senderName + "\nTo: " + toAddress
+ "\nParcel: " + item.desc+item.weight + "\ncost: " + calcCost();
}
}
I am trying to understand stacks with Objects, so I typed this out, but the problem is that I am getting this really weird message that I can't make sense of. It says "Exception in thread "main" java.lang.NoSuchMethodError: Stack.push(Ljava/lang/Object;)V
at TestObjectStack.main(TestObjectStack.java:12)". I googled it, but I still can't figure out what I'm doing wrong. I redid the main method header, but that didn't fix it. Does anyone have any suggestions or insight that I am missing? Thanks a lot!:
public class TestObjectStack
{
public static void main(String[] args)
{
Object o;
Stack test = new Stack();
test.push("Fred");
test.push(20);
test.push(new ThingB("Barney", 42));
Stack copy = new Stack(test);
System.out.println("Stack test: " + test);
System.out.println(test.pop());
System.out.println("Stack test: " + test);
System.out.println("Stack copy: " + copy);
if(test.isEmpty()) System.out.println("Empty");
o = test.pop();
System.out.println(o);
if(o instanceof String)
{
String s = (String) o;
System.out.println("String length = " + s.length());
}
else
System.out.println("Not a String");
if(test.isEmpty()) System.out.println("Empty");
o = test.pop();
System.out.println(o);
if(o instanceof String)
{
String s = (String) o;
System.out.println("String length = " + s.length());
}
else
System.out.println("Not a string");
if(test.isEmpty()) System.out.println("empty");
}
}
class ThingB
{
private String _name;
private int _ID;
public ThingB(String name, int ID)
{
_name = name;
_ID = ID;
}
public String toString()
{
return "Thing B - name - " + _name + " ID = " + _ID;
}
}
class Stack
{
private Object[] _store;
private int _top;
private static final int MAXSIZE = 50;
public Stack()
{
_store = new Object[MAXSIZE];
_top = 0;
}
public Stack(Stack other)
{
_store = new Object[other._store.length];
_top = other._top;
for(int i = 0; i < _top; ++i)
{
_store[i] = other._store[i];
}
}
public boolean isEmpty()
{
return (_top == 0);
}
public void push(Object item)
{
if(_top >= _store.length)
{
Object[] temp = new Object[_store.length+ MAXSIZE];
for(int i = 0; i < _top; ++i)
{
temp[i] = _store[i];
}
_store = temp;
}
_store[_top] = item;
++_top;
}
public Object pop()
{
if(_top == 0) return 0;
--_top;
return _store[_top];
}
public String toString()
{
String s = "";
s = s + "--Top--";
for(int i = _top-1; i >= 0; --i)
{
s = s + " " + _store[i];
}
s = s + "--Bottom--";
return s;
}
}
I executed your code in the IDE: IntelliJ IDEA. And I have the following result:
Stack test: --Top-- Thing B - name - Barney ID = 42 20 Fred--Bottom--
Thing B - name - Barney ID = 42
Stack test: --Top-- 20 Fred--Bottom--
Stack copy: --Top-- Thing B - name - Barney ID = 42 20 Fred--Bottom--
20
Not a String
Fred
String length = 4
empty
Your source code is working fine, maybe you need to adjust your IDE parameters. Try with a simple "Hello World" program.
Best regards,
Alvaro
I have created a class Hotel defined as follows:
import java.util.Random;
public class Hotel {
private Osoba[] tab = new Osoba[100];
public void zamelduj(Osoba os, int num) {
if (tab[num - 1] == null) {
System.out.println("Pokoj o numerze " + num + "jest zajety");
return;
}
tab[num - 1] = os;
}
public void wymelduj(int num) {
tab[num - 1] = null;
}
public void zamienOsoby(int num1, int num2) {
Osoba o = tab[num1 - 1];
tab[num1 - 1] = tab[num2 - 1];
tab[num2 - 1] = o;
}
public void znajdzWolnePokoje() {
for (int i = 0; i < 100; i++) {
if (tab[i] == null) System.out.println(i + 1);
}
}
public void przydzielPokoje50() {
for (int i = 0; i < 50; i++) {
Random r = new Random();
Osoba o = new Osoba();
int num = r.nextInt(100);
tab[num] = o;
}
}
public void wypisz() {
for (int i = 0; i < 100; i++) {
if (tab[i] == null) System.out.println("Pokoj nr. " + (i + 1) + " jest wolny");
else System.out.println("Pokoj nr. " + i + " jest zajety przez " + tab[i].imie + " " + tab[i].nazwisko);
}
}
public static void main(String[] args) {
Hotel h = new Hotel();
//h.przydzielPokoje50();
//h.wypisz();
h.zamelduj(null, 30);
}
}
I also have a class Osoba:
public class Osoba {
public String imie;
public String nazwisko;
Osoba() {
imie = null;
nazwisko = null;
}
Osoba(String imie, String nazwisko) {
this.imie = imie;
this.nazwisko = nazwisko;
}
}
I want to execute the method Zamelduj, which will assign a person (Osoba) to a cell in a table. However, every time I insert something other than null in the following it says that the first argument is not a capable parameter of the method.
h.zamelduj(null, 30);
What am I doing wrong?
I think your problem is that on the line " h.zamelduj(null, 30);" you need to create a new Osoba:
h.zamelduj(new Osoba("o.o", "._.!"), 30);
what happens is that the function is expecting a Osoba, if you give it another thing, it refuses. i hope it helps
You need to create an object of the class hotel (in your class from where you want to call the method type):
Hotel myObjectHotel = new Hotel();
And then you can call the method trough:
myHotelObject. zamelduj(give parameters here);
:)
Update:
Missed the real question. Just focused on the topic. I'm sorry. ;)
In drjava I'm trying to acquire pictures in hold them in the array, and then print out a description of each picture. Right now everything compiles but when I run it has me choose the folder that contains the pictures and then the interactions pane disappears. The code I have so far is in my House app for acquiring the pictures and printing the descriptions is
SSCCEE
HOUSE.java
public class House
{
String owner;
public final static int CAPACITY = 6;
Picture[ ] pictArray = new Picture[CAPACITY];
public House(String pString)
{
this.owner = pString;
}
public String toString()
{
return("The House owned by " + this.owner);
}
public void acquire( int position, Picture pRef )
{
this.pictArray[ position ] = pRef;
}
public void printPictures()
{
for (int i=0; i < this.pictArray.length;i++)
{
System.out.print("The Picture in position " + i + " is ");
System.out.println( this.pictArray[ i ]);
}
}
public void swap( int positionA, int positionB )
{
System.out.println("NOTHING DONE. THIS IS JUST A swap's STUB");
}
public void showOff()
{
System.out.println("NOTHING DONE. THIS IS JUST showOff's STUB");
}
}
Test.java
import java.util.Scanner;
public class Test
{
public static void main(String[] a)
{
House h = new House("Justin Chaisetseree");
Scanner sc = new Scanner(System.in);
FileChooser.pickMediaPath();
for( int i = 0; i < 6; i++)
{
h.acquire(i,new Picture(FileChooser.pickAFile()));
}
h.printPictures();
h.showOff();
Boolean done = false;
while( ! done )
{
System.out.println("Which two do you want to swap?");
System.out.print("Type in two numbers from 0 to ");
System.out.print( 5 );
System.out.println(" or two -1s to stop.");
int userInput1 = sc.nextInt();
int userInput2 = sc.nextInt();
if( userInput1 < 0 || userInput2 < 0)
{
done = true;
}
else
{
h.swap( userInput1, userInput2 );
}
}
h.showOff();
}
}
I've had this problem throughout multiple programs, but I can't remember how I fixed it last time. In the second while loop in my body, the second sentinel value is never read in for some reason. I've been trying to fix it for a while now, thought I might see if anyone had any clue.
import java.text.DecimalFormat; // imports the decimal format
public class Car {
// Makes three instance variables.
private String make;
private int year;
private double price;
// Makes the an object that formats doubles.
public static DecimalFormat twoDecPl = new DecimalFormat("$0.00");
// Constructor that assigns the instance variables
// to the values that the user made.
public Car(String carMake,int carYear, double carPrice)
{
make = carMake;
year = carYear;
price = carPrice;
}
// Retrieves variable make.
public String getMake()
{
return make;
}
// Retrieves variable year.
public int getYear()
{
return year;
}
// Retrieves variable price.
public double getPrice()
{
return price;
}
// Checks if two objects are equal.
public boolean equals(Car c1, Car c2)
{
boolean b = false;
if(c1.getMake().equals(c2.getMake()) && c1.getPrice() == c2.getPrice() &&
c1.getYear() == c2.getYear())
{
b = true;
return b;
}
else
{
return b;
}
}
// Turns the object into a readable string.
public String toString()
{
return "Description of car:" +
"\n Make : " + make +
"\n Year : " + year +
"\n Price: " + twoDecPl.format(price);
}
}
import java.util.Scanner; // imports a scanner
public class CarSearch {
public static void main(String[] args)
{
// initializes all variables
Scanner scan = new Scanner(System.in);
final int SIZE_ARR = 30;
Car[] carArr = new Car[SIZE_ARR];
final String SENT = "EndDatabase";
String carMake = "";
int carYear = 0;
double carPrice = 0;
int count = 0;
int pos = 0;
final String SECSENT = "EndSearchKeys";
final boolean DEBUG_SW = true;
// Loop that goes through the first list of values.
// It then stores the values in an array, then uses the
// values to make an object.
while(scan.hasNext())
{
if(scan.hasNext())
{
carMake = scan.next();
}
else
{
System.out.println("ERROR - not a String");
System.exit(0);
}
if(carMake.equals(SENT))
{
break;
}
if(scan.hasNextInt())
{
carYear = scan.nextInt();
}
else
{
System.out.println("ERROR - not an int" + count);
System.exit(0);
}
if(scan.hasNextDouble())
{
carPrice = scan.nextDouble();
}
else
{
System.out.println("ERROR - not a double");
System.exit(0);
}
Car car1 = new Car(carMake, carYear, carPrice);
carArr[count] = car1;
count++;
}
// Calls the method debugSwitch to show the debug information.
debugSwitch(carArr, DEBUG_SW, count);
// Calls the method printData to print the database.
printData(carArr, count);
// Loops through the second group of values and stores them in key.
// Then, it searches for a match in the database.
**while(scan.hasNext())**
{
if(scan.hasNext())
{
carMake = scan.next();
}
else
{
System.out.println("ERROR - not a String");
System.exit(0);
}
if(carMake.equals(SECSENT))
{
break;
}
if(scan.hasNextInt())
{
carYear = scan.nextInt();
}
else
{
System.out.println("ERROR - not an int" + count);
System.exit(0);
}
if(scan.hasNextDouble())
{
carPrice = scan.nextDouble();
}
else
{
System.out.println("ERROR - not a double");
System.exit(0);
}
Car key = new Car(carMake, carYear, carPrice);
// Stores the output of seqSearch in pos.
// If the debug switch is on, then it prints these statements.
if(DEBUG_SW == true)
{
System.out.println("Search, make = " + key.getMake());
System.out.println("Search, year = " + key.getYear());
System.out.println("Search, price = " + key.getPrice());
}
System.out.println("key =");
System.out.println(key);
pos = seqSearch(carArr, count, key);
if(pos != -1)
{
System.out.println("This vehicle was found at index = " + pos);
}
else
{
System.out.println("This vehicle was not found in the database.");
}
}
}
// This method prints the database of cars.
private static void printData(Car[] carArr, int count)
{
for(int i = 0; i < count; i++)
{
System.out.println("Description of car:");
System.out.println(carArr[i]);
}
}
// Searches for a match in the database.
private static int seqSearch(Car[] carArr, int count, Car key)
{
for(int i = 0; i < count; i++)
{
boolean b = key.equals(key, carArr[i]);
if(b == true)
{
return i;
}
}
return -1;
}
// Prints debug statements if DEBUG_SW is set to true.
public static void debugSwitch(Car[] carArr, boolean DEBUG_SW, int count)
{
if(DEBUG_SW == true)
{
for(int i = 0; i < count; i++)
{
System.out.println("DB make = " + carArr[i].getMake());
System.out.println("DB year = " + carArr[i].getYear());
System.out.println("DB price = " + carArr[i].getPrice());
}
}
}
}
I think this is your problem, but I might be wrong:
Inside your while loop, you have these calls:
next()
nextInt()
nextDouble()
The problem is that the last call (nextDouble), will not eat the newline. So to fix this issue, you should add an extra nextLine() call at the end of the two loops.
What happens is that the next time you call next(), it will return the newline, instead of the CarMake-thing.