不使用 Array.sort 对多维字符串数组进行排序

Question

I am new to Java, but to expand my knowledge of it. Below is a class assignment that I'm having a very, very difficult time completing. I need to create a method that passes in a two dimensional string array and then sorts the array by the second element.

Method sortContacts()

• Declared as a public static method, it should take a two-dimensional String array as a parameter, and an integer value for the number of contacts in the array
• Returns nothing o Sorts the contents of the contact list given as a parameter using the lastName as the sorting field
• You may use any of the sorting mechanisms described in the text (bubble, insertion or selection)
• Key concept: as you implement the sort, the trick is to identify the dimension for the values you are comparing and how they relate to the values from your loops.
• Hints:
• Do not rely on the array's length for your loops, instead use the value from the number of contacts
• Your temp variable will be an array of size 3, String[] temp = new String[3];
• You will need to use the string1.compareTo(string2) method to compare two strings.

Sample data: (first name, last name, phone number)

String [][] contactsArray = { 

        {"Emily","Watson","913-555-0001"},
        {"Madison","Jacobs","913-555-0002"},
        {"Joshua","Cooper","913-555-0003"},
        {"Brandon","Alexander","913-555-0004"},
        {"Emma","Miller","913-555-0005"},
        {"Daniel","Ward","913-555-0006"},
        {"Olivia","Davis","913-555-0007"},
        {"Isaac","Torres","913-555-0008"},
        {"Austin","Morris","913-555-0009"}



public static void sortContact(String[][] contactsArray, int numContacts) {

    String[] temp = new String[3];
    String [] words = contactsArray[3];

    for(int i = 0; i < numContacts-1; i++)
    {
        int smallest = i;
        for(int j = i + 1; j < numContacts-1; j++) 
        {

            //Prints loop variables so I can see them before any action
            System.out.println("First: "+words[j]+" " +"Second "+words[i]);
            if(words[j].compareTo(words[i]) < 0)
                smallest = j;
        }

       //put the new minimum in the i-th position.

        //String temp = words[i];
        words[i] = words[smallest];
        words[smallest] = temp[i];
    }   
}

There are tons of examples for integer arrays but not a lot for string arrays,

Any suggestions are appreciated.

Answer 1

I would suggest you go through the OOPs concept and how to implement them in Java. There are hundreds of books, articles and tutorials online for the same, like https://www.journaldev.com/12496/oops-concepts-java-example , https://beginnersbook.com/2013/04/oops-concepts/ , etc.

As for the answer, you should create a class that extends Comparable interface to represent each of the rows in the 2D array. For example, create a class called Contact that implements Comparable interface. Implement the compareTo method from Comparable interface. Then create a driver class that creates List of Person and call Collections.sort(list).

I have intentionally left the implementations to you as this is your assignment so that you learn by doing instead of somebody else doing them for you.

Please refer the following links for Comparable interface. https://www.geeksforgeeks.org/comparable-vs-comparator-in-java/

Answer 2

You can do like this,:

 for(int i=0;i<numContacts;i++) {
        for(int j=i+1;j<numContacts;j++) {
            if(contactsArray [i][1].compareTo(contactsArray [j][1])>0) {
                String[] temp = contactsArray [i];
                contactsArray [i] = contactsArray [j];
                contactsArray [j] = temp;
            }
        }
  }