Question

我是Java的新手，需要快速回答，所以不要判断我是否搜索不够。所以我有类Antena并尝试创建Controller类，我不能创建数组列表实例。代码尚未完成。有人能解决这个吗？：d 这是控制器类：

package paket;

import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.nio.file.Path; 
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.List;
import java.util.ResourceBundle;
import java.util.Scanner;

import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.Button;
import javafx.scene.control.Label; 
import javafx.scene.control.TextArea;
import javafx.scene.control.TextField;
import javafx.stage.FileChooser; 
import javafx.stage.FileChooser.ExtensionFilter;

public class KontrolaAntene implements Initializable {
private List<Antena> antene= new ArrayList<Antena>();
private int broj;

@FXML
private Button btnIspisi;
@FXML
private Button btnIzlaz;
@FXML
private TextArea taIspis;
@FXML
private TextArea taIspis_izlaz;
@FXML
private Label label1;
@FXML
private Label label2;
@FXML
private Label label3;
@FXML
private TextField tfx;
@FXML
private TextField tfy;

@FXML
void ispisi(ActionEvent event){
    FileChooser fileChooser = new FileChooser();
    fileChooser.setTitle("Izaberi datoteku");
    fileChooser.getExtensionFilters().addAll(
            new ExtensionFilter("Text files","*.txt"),
            new ExtensionFilter("All files","*.txt")
            );

    String pocetakputanja = System.getProperty("user.dir");
    File pocetak = new File(pocetakputanja);

    if(!pocetak.canRead())
    {
        pocetak = new File("C:/");
    }

    fileChooser.setInitialDirectory(pocetak);

    File selectedFile = fileChooser.showOpenDialog(TestAntene.mainStage);

    if(selectedFile == null || selectedFile.getName()!="antene.txt"){
        taIspis.setText("Datoteka antene.txt nije izabrana");
    }
    else{
        taIspis.setText("");
        ispisiFajl(selectedFile);
    }


    }

void ispisiFajl(File selectedFile){
    antene.clear();
    Path put = Paths.get(selectedFile.getPath());
    Charset kod = StandardCharsets.UTF_8;
    Scanner sc;
    try {
        sc = new Scanner(put, kod.name());
        while(sc.hasNextLine()){
        String linija = sc.nextLine();
        String tip = linija.substring(0,linija.indexOf(":")).trim();
        String delovi[]= linija.substring(linija.indexOf(":") + 1,
                    linija.length()).split(", ");
        if(tip == "K"){
        //THIS LINE IS A PROBLEM!
            Antena nova = new Antena(Integer.parseInt(delovi[1].trim()),
                    Integer.parseInt(delovi[1].trim()),Integer.parseInt(delovi[1].trim()));
        }
        }


    } catch (Exception e) {
        // TODO Auto-generated catch block
        taIspis.setText("Datoteka antene.txt nije izabrana");
    }
   }

@FXML
void ispisi_izlaz(ActionEvent event){
    taIspis_izlaz.appendText("Broj antena koje pokrivaju zadato mesto je "+broj);
}

@Override
public void initialize(URL arg0, ResourceBundle arg1) {
    // TODO Auto-generated method stub

}

}

这是Antena班：

package paket;

公共抽象类Antena {

public int x;
public int y;
public int Domet1;
public int Domet2;

public int getX() {
    return x;
}
public void setX(int x) {
    this.x = x;
}
public int getY() {
    return y;
}
public void setY(int y) {
    this.y = y;
}
public int getDomet1() {
    return Domet1;
}
public void setDomet1(int domet1) {
    Domet1 = domet1;
}
public int getDomet2() {
    return Domet2;
}
public void setDomet2(int domet2) {
    Domet2 = domet2;
}
public Antena(int x, int y, int domet1, int domet2) {
    super();
    this.x = x;
    this.y = y;
    Domet1 = domet1;
    Domet2 = domet2;
}   

boolean uDometu(int x, int y)
{

    double rastojanje;
    int x2 = getX();
    int y2 = getY();
    int domet1= getDomet1();
    int domet2= getDomet2();
    if(getDomet2() == 0){
        rastojanje= Math.sqrt((y-y2)*(y-y2)+(x-x2)*(x-x2));
        if((double)getDomet1() >= rastojanje)
            return true;
        else
            return false;
    }
    else
    {
      if((x2==x && y2+domet2>y)||
         (x2==x && y2-domet2<y)||
         (x2+domet1>x && y2==y)||
         (x2-domet1<x && y2==y)){ return true;}
      else if((x2+domet1>=x && y2+domet1>=y)||
              (x2-domet1<=x && y2+domet1<=y)||
              (x2+domet1<=x && y2+domet1>=y)||
              (x2+domet1>=x && y2+domet1<=y))
                {return true;}
      else  return false;
    }
    }

}

Answer 1

您似乎没有正确地比较String（s），并且您无法实例化abstract类。选项¹，

从abstract或

Antenna

创建具体子类并实例化该子类

像

if (tip.equals("K")) { // == "K"){
    Antenna nova = new Antenna(Integer.parseInt(delovi[1].trim()), // ...

请记住然后将“Antena”更改为

public class Antenna { // <-- Not abstract

^{1 _{我还更正了天线的拼写。}}

Answer 2

您标记的行中有2个问题：

Antena是抽象类，无法实例化。这是抽象类的一个非常基本的特征，意味着继承。你应该继承Antena或制作非抽象的
您正在调用Antena的构造函数，并且您将传递3个整数作为参数。但是Antena的唯一构造函数需要4个int

Answer 3

抽象类，无法实例化，antena是抽象类型。删除抽象关键字，它将起作用。

无法实例化数组列表的类型

3 个答案: