java - 从位置类获取 "getDistance"并使用 if 条件在目标类中使用它

Question

//单独文件中的位置类

package tld;
import java.util.*;
public class Location {
private double x;
private double y;
Scanner scan= new Scanner(System.in);

public Location(double x, double y){
x= scan.nextDouble();
y= scan.nextDouble();}

public double getX(){
return x;}

public double getY(){
return y;}

public void setX(double x){
this.x=x;}

public void setY(double y){
this.y=y;}

public String toString(){
return "Location: x= "+getX()+" ; y= "+getY();}

public double getDistance(Location L){ 
 double x1=scan.nextDouble();
 double y1=scan.nextDouble();
 L=new Location(x1,y1);
return (Math.sqrt((Math.pow((x-x1),2))+(Math.pow((y-y1), 2))));}
}

.

//目标类在单独的文件中

package tld;
import java.util.*;
public class Target{
Scanner scan = new Scanner(System.in);
private Location loc;
private double speed;
private String type;
private boolean threat;
private int count = 0;

public Target(double x, double y, double speed){
    x=scan.nextDouble();
    y=scan.nextDouble();
    speed=scan.nextDouble();
    if(speed<500)
         type="Helicopter";
    else type="Jet"; 
    threat = false;
    count++;}

public String getType(){
    return type;}

public double getSpeed() {
    return speed;}

public void setSpeed(double speed) {
    this.speed = speed;}

public Location getLoc() {
    return loc;}

public void setLoc(Location loc) {
    this.loc = loc;}

public boolean isThreat(Location L){
     if(Location.getDistance()<100){
         threat=true;}
     else threat=false;
     return threat;}

public String toString(){
     return "Target is " + getType() + ", speed= " + getSpeed() + "mph, [Location: x=" + Location.x1+ "; y=" + Loc.x + "]";
}}

我的错误在这个类中..在“boolean isThreat 方法”中

.

//主驱动程序在一个单独的文件中，但尚未完成

package tld;
import java.util.*;
public class TLD {
public static void main(String[] args) {
    Location L = new Location(100,200);
System.out.println("please enter 4 targets");
Scanner scan = new Scanner(System.in);
String [] Target=new String[4];
for(int i=0; i<Target.length; i++)
Target[i]=scan.next();


}

}

请注意，我不允许使用高级命令或类

Answer 1

由于 getDistance 不是静态的，因此您需要先拥有 Location 的实例，然后才能调用它。幸运的是，您确实有一个实例。看到类顶部声明的 loc 变量了吗？这就是您所需要的!

所以改变这一行

if(Location.getDistance()<100){

对此:

if(loc.getDistance(L)<100){

“为什么我必须把L放在那里？”你可能会问。那是因为我们正在获取两个位置之间的距离!第一个位置是 loc 但第二个位置是什么？从方法签名来看，我认为您希望参数 L 成为第二个位置。

此外，您的代码中还有很多没有意义的地方。这是我对您想要做什么的猜测:

public class Location {
    private double x;
    private double y;

    public Location(double x, double y){
        this.x = x;
        this.y = y;
    }

    public double getX(){
        return x;
    }

    public double getY(){
        return y;
    }

    public void setX(double x){
        this.x=x;
    }

    public void setY(double y){
        this.y=y;
    }

    public String toString(){
        return "Location: x= "+getX()+" ; y= "+getY();
    }

    public double getDistance(Location L){
        double x1=L.getX();
        double y1=L.getY();
        return (Math.sqrt((Math.pow((x-x1),2))+(Math.pow((y-y1), 2))));
    }
}

public class Target{
    private Location loc;
    private double speed;
    private String type;
    private boolean threat;
    private static int count = 0;

    public Target(double x, double y, double speed){
        loc = new Location(x, y);
        this.speed = speed;
        if(speed<500)
            type="Helicopter";
        else type="Jet";
        threat = false;
        count++;
    }

    public String getType(){
        return type;
    }

    public double getSpeed() {
        return speed;
    }

    public void setSpeed(double speed) {
        this.speed = speed;
    }

    public Location getLoc() {
        return loc;
    }

    public void setLoc(Location loc) {
        this.loc = loc;
    }

    public boolean isThreat(Location L){
        if(loc.getDistance(L)<100){
            threat=true;}
        else threat=false;
        return threat;
    }

    public String toString(){
        return "Target is " + getType() + ", speed= " + getSpeed() + "mph, [Location: x=" + loc.getX()+ "; y=" + loc.getY() + "]";
    }
}