如何使用构造函数初始化每个数组元素时从文件读取和存储对象数组

Question

I am trying to create program that shows 2 outputs to the screen.

The first one being null and the 2nd one, shows values from the input file that was stored in an array of objects.

Here is my code so far:

 javax.swing.JOptionPane; import java.util.Scanner; import java.io.File; public class Testing { public static void main(String[] args) { //error checking for commandline input if(args.length != 1){ System.out.println("Please enter at least one input file into the argument."); //terminates the program if more than 1 is entered System.exit(1); } //make an array of bird objects final Integer SIZE = 9; HawaiiNativeForestBirds array[] = new HawaiiNativeForestBirds[SIZE]; //output array of Nature objects to the screen (should be "null" for all elements) System.out.println("Hawai'i Native Forest Birds "); System.out.println("index element "); for (int i = 0; i < SIZE; i++) { System.out.println(" " + i + " " + array[i] ); System.out.println(); //read from file and store data from file in your Nature array of objects //by initializing each array element using the constructor File file = new File(args[0]); Scanner inputFromFile = null; array[0] = new HawaiiNativeForestBirds("'akiapola'au"," hemignathus munroi"," yellow", 800); array[1] = new HawaiiNativeForestBirds("akepa"," loxxops coccineus"," red", 9301); array[2] = new HawaiiNativeForestBirds("hawai'i creeper"," oreomystis mana"," yellow green", 2501); array[3] = new HawaiiNativeForestBirds("i'iwi"," vestiara conccinea"," red green", 2501); array[4] = new HawaiiNativeForestBirds("apapane"," himatione sanguinea"," white red", 5001); array[5] = new HawaiiNativeForestBirds("hawai'ian amakihi"," hemignathus virens"," yellow brown", 3001); array[6] = new HawaiiNativeForestBirds("hawaii'an hawk"," buteo solitarius"," white gray", 1100); array[7] = new HawaiiNativeForestBirds("puaiohi"," myadestes palmeri"," brown", 125); array[8] = new HawaiiNativeForestBirds("anianiau"," magumma parva"," light yellow", 2000); //use toString() to display the array again with data from input file System.out.println("index name Scientific Name Color Population"); for(int x=0;x<SIZE;x++){ System.out.println(" " + i + " " + array[i]); } }//end of main() method }// end of class LastnameFirstname08 /** * Class HawaiianTheme stores and displays the data for each HawaiianTheme object * * */ class HawaiiNativeForestBirds { // data fields that store each object's data private String name; private String scientificname; private String color; private Integer population; //constructor - used to initialize the three data fields /** * Stores the name,scientific name, color and population of the Hawaiian Birds * This is a Constructor, which is used to Create EAch Object & Initialize DAta Fields. * * @param * @param * @param * @param */ public HawaiiNativeForestBirds(String birdName, String scientificName,String birdColor, Integer birdPopulation) { name = birdName; scientificname = scientificName; color = birdColor; population = birdPopulation; }//end of constructor //toString() method - returns a String with the 4 data fields public String toString() { String output = name +" "+ scientificname + " "+ color +" "+ population; return output; }//end of toString() }//end of class HawaiianTheme 

The only thing missing now is the method that reads from file and stores the array of objects by initializing the arrays.

I'm still no good at combining both of these and as you can see from the code, I don't have the method yet nor I know how the format would look like to combined both.

edit 2: I finally fixed my output . I initiliazed stuff, now how to read from file and store to the array? ;_; Output:

 Hawai'i Native Forest Birds index element 0 null 1 null 2 null 3 null 4 null 5 null 6 null 7 null 8 null 9 null index name Scientific Name Color Population 0 'akiapola'au hemignathus munroi yellow 800 1 akepa loxxops coccineus red 9301 2 hawai'i creeper oreomystis mana yellow green 2501 3 i'iwi vestiara conccinea red green 2501 4 apapane himatione sanguinea white red 5001 5 hawai'ian amakihi hemignathus virens yellow brown 3001 6 oma'o myadester obscurus gray 17001 7 hawaii'an hawk buteo solitarius white gray 1100 8 puaiohi myadestes palmeri brown 125 9 anianiau magumma parva light yellow 2000 

All I want is to show two outputs but I gotta read and store the array of objects for the 2nd output

1.Display HawaiiNativeForestBirds array array[] without initializing elements:

2.Display HawaiiNativeForestBirds array[] again but shows the array values from the file after initializing elements:

edit:

My CSV Content:

birds.csv

Answer 1

I would solve this problem in following way.

Create a HawaiiNativeForestBirds java class

class HawaiiNativeForestBirds {
private String name;
private String scientificname;
private String color;
private Integer population;
public HawaiiNativeForestBirds(){

  }
  public HawaiiNativeForestBirds(String name, String scientificname,
        String color, Integer population) {
    super();
    this.name = name;
    this.scientificname = scientificname;
    this.color = color;
    this.population = population;
  }  


  public String getName() {
    return name;
}
public void setName(String name) {
    this.name = name;
}
public String getScientificname() {
    return scientificname;
}
public void setScientificname(String scientificname) {
    this.scientificname = scientificname;
}
public String getColor() {
    return color;
}
public void setColor(String color) {
    this.color = color;
}
public Integer getPopulation() {
    return population;
}
public void setPopulation(Integer population) {
    this.population = population;
}

  public String toString() {
  String output = name +"     "+ scientificname + "     "+ color +"     "+        population;
  return output;
}      
}

Edit: If you want read a csv file then you cans solve it as below:

Assuming csv file contains data in following format

puaiohi,myadestes palmeri,brown,125
puaiohi,magumma parva,yellow,2000

I have modified Testing class to read the csv file

 public class Testing {

 public static void main(String[] args) {

    String csvFile = "birds.csv";
    String line = "";
    String cvsSplitBy = ",";

    List<HawaiiNativeForestBirds>  listofBirds = new ArrayList<HawaiiNativeForestBirds>();
    try (BufferedReader br = new BufferedReader(new FileReader(csvFile))) {

        while ((line = br.readLine()) != null) {

            // use comma as separator
            String[] bird = line.split(cvsSplitBy);
            HawaiiNativeForestBirds Hawaiinbird= new HawaiiNativeForestBirds(bird[0],bird[1],bird[2],Integer.valueOf(bird[3]));
            listofBirds.add(Hawaiinbird);
        }

    } catch (IOException e) {
        e.printStackTrace();
    }
// First display null values
 HawaiiNativeForestBirds[]  hbirds=new        HawaiiNativeForestBirds[listofBirds.size()];
    System.out.println("index   " + "element   ");  
    int i=0;
    for (HawaiiNativeForestBirds hbird:hbirds){
        i++;
        System.out.println(i+"   "+hbird);
        }
    // Now display actual values
    hbirds= listofBirds.toArray(new HawaiiNativeForestBirds[listofBirds.size()]);

    System.out.println("index   " + "name   "+ "Scientific Name    "+ "Color   " + "Population   ");        
    i=0;
    for (HawaiiNativeForestBirds hbird:hbirds){
        i++;
        System.out.println(i+"   "+hbird.toString());
        }
 }
 }

Note: HawaiiNativeForestBirds class would remain as it is.

Answer 2

Try reading in each String and storing it into its own index in a array of Strings. Then check out this algorithm and see if it works. I am sure this is not the best way to handle the situation, but I am in class and thought I would give it a intuitive shot. I am going off of the base that your constructor takes 4 parameters, and also assuming that the parameters in the txt file are in order of how they would be put into the constructor. You will also have to cast the 4th parameter into a int so it matches the expected argument type for your constructor.

//Create String array and use for loop to fill temp array with words from txt file
temp[i] = scan.next()
for(int i = 0; i < temp.length; i++) {
if (i != 0) {
i = i + 3;
HawaiiNativeForestBirds[i - (3*i/4)] = new HawaiiNativeForestBirds(temp[(i-4)+4], temp[(i-4)+5], temp[(i-4)+6], temp[(i-4)+7)];

}
else {
HawaiiNativeForestBirds[i] = new HawaiiNativeForestBirds(temp[i],temp[i+1], temp[i+2], temp[i+3]);
}
}