I have an action listener that calls some methods and one of those methods counts the number of times that a loop inside of another method is run. The problem I am having is that the counter just adds to itself (I understand why I just don't know how to fix it) rather than resetting back to 0.
Here is my action listener code.
public double computeIterative(double n) throws InvalidInput {
int a=1, b=2;
int result = 0;
if (n>=0) {
if(n==0)return 0;
if(n==1)return 1;
if(n==2)return 2;
for(int i = 3; i <= n; i++) {
result = a+(2*b);
a=b;
b = result;
this.getEfficiency();
}
} else{
throw new InvalidInput();
}
return result;
}
ActionListener that calls methods and sets text:
public void actionPerformed(ActionEvent e) {
int n = Integer.parseInt(nField.getText());
//Try Catch for Iterate Radio Button
if (iterateBtn.isSelected()){
try {
double result = sequence.computeIterative(n);
int efficiency = sequence.getEfficiency();
rField.setText(Double.toString(result));
eField.setText(Integer.toString(efficiency));
}
catch (InvalidInput ex) {
}
}
The getEfficiency method counts how many times the loop inside computeIterative method is run and then sets it to a textField.
Here is my getEfficiency method:
public int getEfficiency() {
efficiency++;
return efficiency;
}
Now obviously this will just keep adding onto itself, and I am sure that I am looking way too hard for a solution but I just cant figure it out.
Basically, after the try, catch, I need to set efficiency to 0 so that the next time the computeIterative(n) method is called, I get a proper reading.
You could simply add a method resetEfficiency():
public int resetEfficiency() {
efficiency = 0;
}
And then call it at the beginning of computeIterative():
public double computeIterative(double n) throws InvalidInput {
this.resetEfficiency();
//rest of code goes here
//....
}
(Of course I'm assuming this is not multi-threaded or anything).
public double computeIterative(double n) throws InvalidInput {
int a=1, b=2;
int result = 0;
this.resetEfficiencyCounter(); //Call Reset if Number Got Invalid.
if (n>=0) {
if(n==0)return 0;
if(n==1)return 1;
if(n==2)return 2;
for(int i = 3; i <= n; i++) {
result = a+(2*b);
a=b;
b = result;
this.getEfficiency();
}
} else{
throw new InvalidInput();
}
return result;
}
add new Function Named resetEfficiencyCounter().
private void resetEfficiencyCounter(){
this.efficiency = 0;
}
Related
I was asked to program a method that receives a scanner, and returns a sorted array of words which contain only letters, with no repetitions (and no bigger in length than 3000). Then, I was asked to program a method that checks whether a certain given string is contained in a given vocabulary. I used a simple binary search method.
This is what I've done:
public static String[] scanVocabulary(Scanner scanner){
String[] array= new String[3000];
int i=0;
String word;
while (scanner.hasNext() && i<3000) {
word=scanner.next();
if (word.matches("[a-zA-Z]+")){
array[i]=word.toLowerCase();
i++;
}
}int size=0;
while (size<3000 && array[size]!=null ) {
size++;
}
String[] words=Arrays.copyOf(array, size);
if (words.length==0 || words.length==1) {
return words;
}
else {
Arrays.sort(words);
int end= removeDuplicatesSortedArr(words);
return Arrays.copyOf(words, end);
}
}
private static int removeDuplicatesSortedArr(String[] array) { //must be a sorted array. returns size of the new array
int n= array.length;
int j=0;
for (int i=0; i<n-1; i++) {
if (!array[i].equals(array[i+1])) {
array[j++]=array[i];
}
}
array[j++]=array[n-1];
return j;
}
public static boolean isInVocabulary(String[] vocabulary, String word){
//binary search
int n=vocabulary.length;
int left= 0;
int right=n-1;
while (left<=right) {
int mid=(left+right)/2;
if (vocabulary[mid].equals(word)){
return true;
}
else if (vocabulary[mid].compareTo(word)>0) {
right=mid-1;
}else {
right=mid+1;
}
}
return false;
}
while trying the following code:
public static void main(String[] args) {
String vocabularyText = "I look at the floor and I see it needs sweeping while my guitar gently weeps";
Scanner vocabularyScanner = new Scanner(vocabularyText);
String[] vocabulary = scanVocabulary(vocabularyScanner);
System.out.println(Arrays.toString(vocabulary));
boolean t=isInVocabulary(vocabulary, "while");
System.out.println(t);
System.out.println("123");
}
I get nothing but-
[and, at, floor, gently, guitar, i, it, look, my, needs, see, sweeping, the, weeps, while]
nothing else is printed out nor returned. Both functions seem to be working fine separately, so I don't get what I'm doing wrong.
I would be very happy to hear your thoughts, thanks in advance :)
This has nothing to do with the console. Your isInVocabulary method is entering an infinite loop in this block:
if (!isInVocabulary(vocabulary, "while")) {
System.out.println("Error");
}
If you were to debug through isInVocabulary, you would see that after a few iterations of the while loop,
left = 0;
right = 2;
mid = 1;
if (vocabulary[mid].equals(word)){
// it doesn't
} else if (vocabulary[mid].compareTo("while") > 0) {
// it doesn't
} else {
right = mid + 1;
// this is the same as saying right = 1 + 1, i.e. 2
}
So you'll loop forever.
I know that the variable maxreps isn't in the scope of my main method so I wanted it call it by creating an object, but it still isn't able to get maxreps.
How could I fix this?
public class LUIS{
public void james(){
int current=1;
int maxreps=1;
String adriana = "aabbddddnsspkrrgg";
for(int a=0; a<adriana.length(); a++){
if(adriana.charAt(a) == adriana.charAt(a+1)){
current++;
if(maxreps>=current){
maxreps=current;
}
}
}
}
public static void main(String[] args){
LUIS fritz = new LUIS();
final int drei = fritz.james;
System.out.println(maxreps);
}
}
As you noted, scoping prevents seeing a variable defined in a different scope. You can resolve your particular issue by returning the value
public int james(){ // <-- change from void to an int return
int current=1;
int maxreps=1;
String adriana = "aabbddddnsspkrrgg";
for(int a=0; a<adriana.length(); a++){
if(adriana.charAt(a) == adriana.charAt(a+1)){
current++;
if(maxreps>=current){
maxreps=current;
}
}
}
return maxreps; // <-- return the value
}
And then in the main method set a variable to the returned value.
Alternatively, you can define it as a class variable, but there are reasons to avoid doing so -- globals are generally bad.
1) final int drei = fritz.james; cannot compile. You cannot invoke a method in this way (that is without ()).
2) Besides, the james() method should have a more meaningful name.
This method computes the max series of a same character. So, you could call it computeMaxSeries()
3) And instead being a void method, you could return the max series number.
4) Besides this :
for (int a = 0; a < adriana.length(); a++) {
if (adriana.charAt(a) == adriana.charAt(a + 1)) {
will throw a StringIndexOutOfBoundsException as adriana.charAt(a + 1) refers to an index beyond the valid limit of the String length.
You should rather iterate until the last index -1 :
for (int a = 0; a < adriana.length()-1; a++) {
5) At last this is not consistent since you update maxreps by relying on maxreps instead of current :
if(maxreps>=current){
maxreps=current;
}
You should rather write :
if (current >= maxreps) {
maxreps = current;
}
So, finally the method would be :
public int computeMaxSeries(){
int current=1;
int maxreps=1;
String adriana = "aabbddddnsspkrrgg";
for(int a=0; a<adriana.length()-1; a++){
if(adriana.charAt(a) == adriana.charAt(a+1)){
current++;
if (current >= maxreps) {
maxreps = current;
}
}
}
return maxreps;
}
Now you can do :
final int maxreps = fritz.computeMaxSeries();
System.out.println(maxreps);
I have a function that is searching for max number in the array. I want to make the function to search for more than one word that is entered from console.
As example I enter two words(car,ride) they're added to array and then "surasti" function is comparing them if they're in the array.
I have tried to do it on my own, but I'm a started and it seems too hard :(
Function that is searching:
public static produktas[] surasti (produktas G[], int n){
produktas A[] = new produktas[1];
produktas max = G[0];
for (int i=1; i<n; i++)
if (max.gautiSvori()<G[i].gautiSvori()) max = G[i];
A[0]=max;
return A;
}
The code that is calling that function (A is the array that you have to search in.):
case 5:
B = surasti(A, n);
System.out.println("Sunkiausias gyvunas yra:");
spausdinti_sar_ekrane(B, B.length);
break;
The produktas class:
class produktas {
private String pavadinimas;
private String salis;
private Double svoris;
private Double kaina;
produktas() {}
produktas(String pav, String salis, double svoris, double kaina){
pavadinimas = pav;
this.salis = salis;
this.svoris = svoris;
this.kaina = kaina;
}
public String gautiPav (){
return pavadinimas;
}
public String gautiSali (){
return salis;
}
public double gautiSvori (){
return svoris;
}
public double gautiKaina (){
return kaina;
}
}
When I try to change the function to this (don't know if its working fine, can't test it):
public static produktas[] surasti (produktas G[], int n){
try{
BufferedReader in = new BufferedReader (new InputStreamReader (System.in));
produktas A[] = new produktas[5];
for (int j=0; j<5; j++){
System.out.println("Kokio produkto ieskosime?");
String found = in.readLine();
for (int i=1; i<n; i++){
if (found.equals(G[i].gautiPav())){
A[j] = G[i];
}
}
}
return A;
} catch(IOException ie){
ie.printStackTrace();
}
}
When I try this code I get this error at public static produktas[] surasti (produktas G[], int n){ line:
This method must return a result of type produktas[]
For the correctly complied code update your method to have a return in catch block as well.
public static produktas[] surasti(produktas G[], int n) {
try {
BufferedReader in = new BufferedReader(new InputStreamReader(
System.in));
produktas A[] = new produktas[5];
for (int j = 0; j < 5; j++) {
System.out.println("Kokio produkto ieskosime?");
String found = in.readLine();
for (int i = 1; i < n; i++) {
if (found.equals(G[i].gautiPav())) {
A[j] = G[i];
}
}
}
return A;
} catch (IOException ie) {
ie.printStackTrace();
return null; // Expected return from catch block
}
}
To understand the issue properly start using IDE like eclipse rather than simply using a notepad and compiling code through java/javac
A more suitable code would be like as below. Type q in console when u want to exit from the program.
public static produktas[] surasti(produktas G[], int n) {
BufferedReader consoleReader = null;
produktas produktasFound[] = new produktas[5]; // Initalize array to store the produkt found
try {
consoleReader = new BufferedReader(new InputStreamReader(System.in));
boolean exit = false;
produktas produktasFound[] = new produktas[5];
int j = 0;//current produktFound index
while (!exit) {
System.out.println("Kokio produkto ieskosime?");
String produktPav = in.readLine();
if ("q".equals(produktPav)) {
exit = true;
} else {
for (int i=1; i<n; i++){
if (found.equals(G[i].gautiPav())){
A[j] = G[i];
j++;
}
}
}
if(j == 5)
exit = true;
}
return produktasFound; // return all the 5 produktas found
} catch (IOException e) {
e.printStackTrace();
} finally {
if (consoleReader != null) {
try {
consoleReader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
return produktasFound; //If no produkt is found from the array returned is blank
}
Your comparison operator is not correct. Try the following code :
public static produktas surasti(produktas G[]) {
produktas max = G[0];
for (int i = 0; i < G.length; i++) {
if (max.gautiSvori() < G[i].gautiSvori()) {
max = G[i];
}
}
return max;
}
You need to pass the array and set the first element of the array as the maximum as by default first. Next iterate through the array and check whether there is a produktas with a higher value of svoris. If so, change the max to point to this new produktas. At the end of the for loop, you will now have the max set to the produktas with the highest value of svoris.
There are few things in the code that you can fix for better quality code.
You don't need to pass the array size to the surasti method. We can just do a G.length (in the code above I have done that).
Best practice is to user Camel case for Java classes. Therefore instead of produktas, use Produktas
Use meaningful names for variables instead of A, G, etc
I want to know how to tell if an int has been changed (during the program).
Like with an if statement.
int i = 2;
int a = 1;
while(1 < 2) {
if(i % 100 == 0) i++;
}
if(i //Then checks if it changed) {
System.out.println("Changed :D");
}
Is there a way to tell if the variable i is changed DURING the program?
Since this is Java, are these variables data members of a class? In that case give them private access and provide getters and setters. Your setter can notify you if you so desire.
int i = 0;
boolean valueChanged = false;
while(some good condition) {
if (i % 100 == 0) {
i++;
valueChanged = true;
}
}
if(valueChanged) {
System.out.println("Changed :D");
}
// Your int variable
int i = 0;
// A scratch variable
int prev_value_of_i = i;
// Call this code to check whether i has changed since last call
if(i != prev_value_of_i) {
System.out.println("Changed :D");
prev_value_of_i = i;
}
Keep track of the original value of i in a separate variable and compare i to that?
This seems redundant, since the programmer should know when and where values are stored. If you don't, maybe step through with a debugger? #shoover's answer is the most flexible, handling however many unexpected times you might change the value without requiring adding lines of code inside your infinite loop.
class TalkativeInt{
private int x;
TalkativeInteger(int x){
this.x = x;
}
public void set(int a){
System.out.println("Changed!! "+x+" to "+a);
x = a;
}
public int get(){
//System.out.println("Accessed - that tickles");
return x;
}
}
Hi for my java revision I'm going through past paper questions and I'm stuck. I'm given this code:
class FriendFinderThread extends Thread {
// number of FriendBook friends
int numFriends = 0;
public void run() {
// join, then leave FriendBook
FriendBook.join(this);
try { Thread.sleep(10000); }
catch (InterruptedException(ie) {}
FriendBook.leave(this);
}
}
class FriendBook {
// list of FriendBook members
static Vector<FriendFinderThread> members =
new Vector<FriendFinderThread>();
static void join(FriendFinderThread f) {
// add a new friend to all existing members
int size = members.size();
for (int i = 0; i < size; i++) {
members.elementAt(i).numFriends++;
}
f.numFriends = size; // new member’s friends
members.add(f); // add to list of members
}
static void leave(FriendFinderThread f) {
members.remove(f); // remove from list
int size = members.size();
for (int i = 0; i < size; i++) {
members.elementAt(i).numFriends--;
}
}
public static void main() {
for (int n = 0; n < 100; n++) {
new FriendFinderThread().start();
}
}
}
I'm having real trouble understanding what is going on, could someone please explain what is happening in the code and how the code could have problems with interference.
Thank you
At some point one thread will call join. This uses members.size() and accesses each element in members. While doing so another member will leave (the later threads will be slower as they loop over more elements, so at some point there will be more leaving than joining). This means that members.elementAt(members.size()-1) will throw an error.