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Java- function seems to mess up the console, nothing will be printed out after calling the function

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.

Writing an equals method to compare two arrays

I have the following code, I believe something is off in my equals method but I can't figure out what's wrong.
public class Test {
private double[] info;
public Test(double[] a){
double[] constructor = new double[a.length];
for (int i = 0; i < a.length; i++){
constructor[i] = a[i];
}
info = constructor;
}
public double[] getInfo(){
double[] newInfo = new double[info.length];
for(int i = 0; i < info.length; i++){
newInfo[i] = info[i];
}
return newInfo;
}
public double[] setInfo(double[] a){
double[] setInfo = new double[a.length];
for(int i = 0; i < a.length; i++){
setInfo[i] = a[i];
}
return info;
}
public boolean equals(Test x){
return (this.info == x.info);
}
}
and in my tester class I have the following code:
public class Tester {
public static void main(String[] args) {
double[] info = {5.0, 16.3, 3.5 ,79.8}
Test test1 = new Test();
test 1 = new Test(info);
Test test2 = new Test(test1.getInfo());
System.out.print("Tests 1 and 2 are equal: " + test1.equals(test2));
}
}
the rest of my methods seem to function correctly, but when I use my equals method and print the boolean, the console prints out false when it should print true.

You are just comparing memory references to the arrays. You should compare the contents of the arrays instead.
Do this by first comparing the length of each array, then if they match, the entire contents of the array one item at a time.
Here's one way of doing it (written without using helper/utility functions, so you understand what's going on):
public boolean equals(Test x) {
// check if the parameter is null
if (x == null) {
return false;
}
// check if the lengths are the same
if (this.info.length != x.info.length) {
return false;
}
// check the elements in the arrays
for (int index = 0; index < this.info.length; index++) {
if (this.info[index] != x.info[index]) {
return false;
} Aominè
}
// if we get here, then the arrays are the same size and contain the same elements
return true;
}
As #Aominè commented above, you could use a helper/utility function such as (but still need the null check):
public boolean equals(Test x) {
if (x == null) {
return false;
}
return Arrays.equals(this.info, x.info);
}

How do I call a variable in another method?

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);

Java Arrays[] - Assigning Specific Elements in a For Loop to Certain Values

I was attempting to write some code for a program in BlueJ (Java) that lists bags and adds and removes items from those bags, that sort of thing. Then I got stuck in the first class; I couldn't get to add an item to the bag properly as you can notice below in the addItem() method; it keeps adding String s to every null element in the array rather the first encountered. Any help would be tremendously appreciated.
Best wishes & many thanks,
Xenos
public class Bag1 {
private String[] store; // This is an array holding mutlitple strings.
public Bag1(int storageCapacity) {
store = new String[storageCapacity];
} // That was the primitive array constructor.
public boolean isFull() {
boolean full = true;
for(int i = 0; i < store.length; i++) {
if(store[i] == null) {
full = false;
}
}
return full;
} // The method above checks if the bag is full or not, and returns a boolean value on that basis.
public void add(String s) {
for(int i = store.length; i >= 0; i--) {
if(store[i] == null) {
store[i] = s;
}
}
}
}

You should exit the loop after finding the first empty spot :
public void add(String s)
{
for(int i=store.length-1; i>=0; i--) { // note the change in the starting index
if(store[i]==null) {
store[i] = s;
break;
}
}
}

Searching through an Array of Objects

I'm attempting to return the index of where an object appears in an array of objects.
public static int search(WordCount[] list,WordCount word, int n)
{
int result = -1;
int i=0;
while (result < 0 && i < n)
{
if (word.equals(list[i]))
{
result = i;
break;
}
i++;
}
return result;
}
WordCount[] is the array of objects.
word is an instance of WordCount.
n is the number of objects in WordCount[]
It runs, but isn't returning the index correctly. Any and all help is appreciated. Thanks for your time.
CLASS
class WordCount
{
String word;
int count;
static boolean compareByWord;
public WordCount(String aWord)
{
setWord(aWord);
count = 1;
}
private void setWord(String theWord)
{
word=theWord;
}
public void increment()
{
count=+1;
}
public static void sortByWord()
{
compareByWord = true;
}
public static void sortByCount()
{
compareByWord = false;
}
public String toString()
{
String result = String.format("%s (%d)",word, count);
return result;
}
}
How I'm calling it...
for (int i=0;i<tokens.length;i++)
{
if (tokens[i].length()>0)
{
WordCount word = new WordCount(tokens[i]);
int foundAt = search(wordList, word, n);
if (foundAt >= 0)
{
wordList[foundAt].increment();
}
else
{
wordList[n]=word;
n++;
}
}
}
}

By default, Object#equals just returns whether or not the two references refer to the same object (same as the == operator). Looking at what you are doing, what you need to do is create a method in your WordCount to return word, e.g.:
public String getWord() {
return word;
}
Then change your comparison in search from:
if (word.equals(list[i]))
to:
if (word.getWord().equals(list[i].getWord()))
Or change the signature of the method to accept a String so you don't create a new object if you don't have to.
I wouldn't recommend overriding equals in WordCount so that it uses only word to determine object equality because you have other fields. (For example, one would also expect that two counters were equal only if their counts were the same.)
The other way you can do this is to use a Map which is an associative container. An example is like this:
public static Map<String, WordCount> getCounts(String[] tokens) {
Map<String, WordCount> map = new TreeMap<String, WordCount>();
for(String t : tokens) {
WordCount count = map.get(t);
if(count == null) {
count = new WordCount(t);
map.put(t, count);
}
count.increment();
}
return map;
}

This method is probably not working because the implementation of .equals() you are using is not correctly checking if the two objects are equal.
You need to either override the equals() and hashCode() methods for your WordCount object, or have it return something you want to compare, i.e:word.getWord().equals(list[i].getWord())

It seems easier to use:
public static int search(WordCount[] list, WordCount word)
{
for(int i = 0; i < list.length; i++){
if(list[i] == word){
return i;
}
}
return -1;
}
This checks each value in the array and compares it against the word that you specified.

The odd thing in the current approach is that you have to create a new WordCount object in order to look for the count of a particular word. You could add a method like
public boolean hasEqualWord(WordCount other)
{
return word.equals(other.word);
}
in your WordCount class, and use it instead of the equals method:
....
while (result < 0 && i < n)
{
if (word.hasEqualWord(list[i])) // <--- Use it here!
{
....
}
}
But I'd recommend you to rethink what you are going to model there - and how. While it is not technically "wrong" to create a class that summarizes a word and its "count", there may be more elgant solutions. For example, when this is only about counting words, you could consider a map:
Map<String, Integer> counts = new LinkedHashMap<String, Integer>();
for (int i=0;i<tokens.length;i++)
{
if (tokens[i].length()>0)
{
Integer count = counts.get(tokens[i]);
if (count == null)
{
count = 0;
}
counts.put(tokens[i], count+1);
}
}
Afterwards, you can look up the number of occurrences of each word in this map:
String word = "SomeWord";
Integer count = counts.get(word);
System.out.println(word+" occurred "+count+" times);