Search an ArrayList with multiple fields using only one field from a different ArrayList

Question

If there is an ArrayList for moviesAvailable and the list takes title, year, genre, price. How can I get a list of movies using an ArrayList of genres?

There is a toString method in the Movie class that prints out the movies. When I run the code everything past the if statement doesn't run because the condition is returned as false.

You can clearly see that you are calling the "equals" method of Genre, but you didn't override it, so you are using the default one, which is wrong. — vc73
– vc73, Commented May 10, 2019 at 14:19

ruohola · Accepted Answer · 2019-05-10 14:46:21Z

1

You need to override equals() in your Genre class, so that you can compare instances of that class to each other.

Here's a quick implementation, which can easily be extended for additional functionality:

@Override
public boolean equals(Object o) {
    if (!(o instanceof Genre)) {
        return false;
    }
    return ((Genre) o).name.equals(this.name);
}

edited May 10, 2019 at 14:46

answered May 10, 2019 at 14:20

ruohola

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4 Comments

Samuel Philipp Over a year ago

Your method also is not null save. new Genre(null).equals(new Genre(null)) throws a NullPointerException.

ruohola Over a year ago

@SamuelPhilipp "Here's a quick implementation, which can easily be extended for additional functionality"

T Dizzle Over a year ago

This method works, is this the only way to solve the problem or there there anything I can change in the code to make it work?

ruohola Over a year ago

@TDizzle Overriding the equals() method is exactly what your code needed.

Bhushan Kawadkar · Accepted Answer · 2019-05-13 08:37:49Z

0

You need to override equals method in Genre class to make if condition working, see below code

private String name;

Genre(String name){
    this.name = name;
}
public boolean hasType(String genre) {

    return genre.equals(this.name);
}

public boolean equals(Object o) {
   if (!(o instanceof Genre)) {
      return false;
   }
   return this.name.equals(((Genre)o).name);
}

edited May 13, 2019 at 8:37

answered May 10, 2019 at 14:19

Bhushan Kawadkar

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1 Comment

vc73 Over a year ago

a better implementation would be: return (o instanceof Genre) ? ((Genre) o).name.equals(this.name) : false;

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