CODEWITHSUNDEEP
javaarrayssearcharraylist
Niklas
Niklas

Reputation: 9

Find string value in ArrayList with own class

this is my first question. Im a studying business administration and started to learn java just for fun. I'm doing the MOOC course from a finnish university. I am at exercise 101. I have to program a library with a search function for books. One can either search by title, publisher or year.

My only ideas were those (that did not work):

public ArrayList<Book> searchByPublisher(String publisher){
      ArrayList<Book> found = new ArrayList<Book>();
         if (bibo.contains(publisher)){
         found.add(bibo.get(bibo.indexOf(publisher)));              
            }            
         return found;

or:

public ArrayList<Book> searchByTitle(String title){
         ArrayList<Book> found = new ArrayList<Book>();
         String [] neueListe = new String[bibo.size()];
         for (int i = 0; i < bibo.size(); i++){
             neueListe[i] = bibo.get(i).toString();
             found.add(neueListe[i].toString());
         }
         return found;

"bibo" is the ArrayList with the books.

I've searched the internet for ideas and solutions and of course came across several on GitHub. But every code I found used the same idea: 

for(Book i : this.bibo){
        if(StringUtils.included(i.title(), title)){
            found.add(i);
        }

In the course there was never used the StringUtils.included and my NetBeans version doesn't know it.

Where the heck is my error in reasoning?

Thanks a lot already in the first place :-)

Upvotes: 0

Views: 124

Answers (4)

Rodrigo Jo&#227;o Bertotti
Rodrigo Jo&#227;o Bertotti

Reputation: 5481

StringUtils is a class from the org.apache.commons.lang library

  1. Download the latest binary .zip file from the apache link (currently commons-lang3-3.5-bin.zip): https://commons.apache.org/proper/commons-lang/download_lang.cgi
  2. Create a "lib" folder in your NetBeans directory enter image description here
  3. Copy only the .jar file of the zip folder and past it into the lib directory that you created
  4. Open NetBeans, Right Click on your Project > Proprieties > Libraries > Add JAR/Folder
  5. Select "Relative Path" and select the jar file that you pasted into your library folder

Upvotes: 0

Davide Spataro
Davide Spataro

Reputation: 7482

The problem in 

public ArrayList<Book> searchByPublisher(String publisher){
      ArrayList<Book> found = new ArrayList<Book>();
         if (bibo.contains(publisher)){
             found.add(bibo.get(bibo.indexOf(publisher)));              
         }            
         return found;

is that you are asking if bibo contains a String while you should ask if it contains a book which publisher field equals to that String (the input to searchByPubisher). 

public ArrayList<Book> searchByPublisher(String publisher){
      ArrayList<Book> found = new ArrayList<Book>();
       for(Book b: bibo){
        if(b.getPublisher().equals(publisher))
         found.add(b);              
         }            
         return found;
}

The searchByTitle function can be implemented similarly.

I would also mention that you can also use Streams to do the job. (Since you are learning java) something like the following should be enough to let you make it work by yourself:

List<Book> found = 
    bibo.stream()
                .filter(b -> t.getPublisher().equals(publisher))
                .collect(toList());

Hope this helps.

Upvotes: 0

Mick Blind
Mick Blind

Reputation: 21

I would do it this way. 

public ArrayList<Book> searchByTitle(String title){
     ArrayList<Book> found = new ArrayList<Book>();
     for (Book book: bibo) {
         if(book.title.contains(title)) {
              found.add(book);
         }
     }
     return found;

You could also look at the Java 8 Streams and the filter functions when you have more java experience. Java 8 Streams example

Upvotes: 0

m.ghoreshi
m.ghoreshi

Reputation: 852

The StringUtils is a third part library form Apache Commons Lang. if you want to use this class you should add the Apache Commons Lang to your project in the Netbeans.
This tutorial shows how to add Apache Commons in Netbeans: https://www.satollo.net/netbeans-apache-commons-and-commons-javadoc-for-auto-completion

Upvotes: 1

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