Java getName(字符串名称)

Question

I am extremely new to Java programming only been at it a few weeks and I have this question of traversing a linked list to find a dog with a matching name. I have made an attempt at what I need but I am struggling to understand the traversal.

Note: I also have a public dog head; variable at the top.

Basically what it needs to do is:

Traverse LinkedList to find a dog with a matching name, if a dog isn't found the return null.

    public Dog getName(String name) {

    Dog name = head;
    int index;

    while(index > 0) {
        index--;
        name = name.next;
    }

    if (name == null)
    {
       return null
    }
        return name;
}

Answer 1

public Dog getName(String name) {

    String dogName = name;
    String listCurrentValue = listOfDogNames //Add your list of dog names here

    While(listOfDogNames.next()){
    If (dogName.equals(listCurrentValue)){ 
        //FOUND MATCH
     }
    Else
       //NO MATCH
     }
    return name;
}

Answer 2

Like localplutonium says, strings shouldn't be compared with ==, but rather with .equals(). Also, i see that you use index in your while loop, but you never assign index to a starting value. There is an int variable called index, but it doesn't have a value, so it's impossible to decrement it.

Answer 3

I found several cosmetic issues in this code: public Dog getName(String name) { // if string name parameter is not used, then why passing it as parameter? ???? Dog name = head; int index;

while(index > 0) {
    index--;
    name = name.next;  //name.next should be name.getNext(); 

}
//  this check is redundant and not need it:
// if null return null else return name??? 
// so you are in fact returning name value no matter what...

if (name == null)
{
   return null
}
    return name;

}

Answer 4

This is homework (obviously) so I can't spoon feed an answer you can hand in, but I can try to create one that is useful and perhaps teaches you something new -- for example the use of collection streams.

You can traverse a collection using streams and not know or care about how the collection does the traversing, use a filter to select out the item of interest and then return it or null if nothing is found with an expression similar to:

public static Dog getDog(String name) {
    // given a collection called dogs
    return dogs.stream()    // get the collection's stream
            .filter(d -> d.getName().equals(name))   // filter on the name text
            .findFirst()    // find the first match and return it
            .orElse(null);    // or else return null
}

For example:

import java.util.LinkedList;
import java.util.List;

public class TestDog {
    private static List<Dog> dogs = new LinkedList<>();

    public static void main(String[] args) {

        String[] names = { "Fido", "Bingo", "Yeller", "Pluto", "Lassie", "Cujo", "Fang", "Rowf",
                "Scamper", "Lady", "Sparky", "Toto", "Bandid", "Beauregard", "Bowser", "Cerberus",
                "Daisy", "Duke", "Fred", "Hellhound", "Rex", "Scamp", "Snoopy" };

        for (String name : names) {
            dogs.add(new Dog(name));
        }

        System.out.println(getDog("Toto"));       
        System.out.println(getDog("Meow"));
    }

    public static Dog getDog(String name) {
        return dogs.stream()
                .filter(d -> d.getName().equals(name))
                .findFirst()
                .orElse(null);
    }
}

public class Dog {
    private String name;

    public Dog(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

    @Override
    public String toString() {
        return "Dog [name=" + name + "]";
    }

}