将我的对象返回到HashSet
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我几乎完全失明了，我正在努力学习Java。我告诉你这是因为我很难理解概念，因为我的残疾。
我的问题：在这个特定的类中，我正在返回一个我希望存储在某个地方的对象，以后再被调用。我不熟悉Collections，但我相信（我认为？）HashSet是我想在这里实施的Set的类型。我是否能够这样做，并在创建后从另一个类调用这个对象集合？
我对Java很新，所以我不确定我是否有效地解释了我的问题。请不要犹豫，要求澄清！
重要提示：我不允许任何重复的airCode，HashSet会以某种方式处理它吗？
public class A8AirlineAircraftData {
private String airName; //these are all showing a warning saying 'Field ____ can be final'
private String airCode;
private String airCraft;
private int firstClass;
private int busiClass;
private int econClass;
//public String toStringAirLine(){return "airname is:" + airName + ", aircode is: "+airCode;}
public A8AirlineAircraftData(String airName, String airCode, String airCraft, int firstClass, int busiClass, int econClass) {
this.airName = airName;
this.airCode = airCode;
this.airCraft = airCraft;
this.firstClass = firstClass;
this.busiClass = busiClass;
this.econClass = econClass;
}
public static A8AirlineAircraftData AddAirline(Scanner sc) {
sc.nextLine();
System.out.println("Please enter the Airline name:");
String airName = sc.nextLine();
System.out.println("Please enter the Airline code:");
String airCode = sc.nextLine();
System.out.println("Please enter the Delta Aircraft:");
String airCraft = sc.nextLine();
System.out.println("Please enter the first class seat capacity:");
int firstClass = sc.nextInt();
System.out.println("Please enter the business class seat capacity:");
int busiClass = sc.nextInt();
System.out.println("Please enter the economy class seat capacity:");
int econClass = sc.nextInt();
System.out.println("Airline name: " + airName);
System.out.println("Airline code: " + airCode);
System.out.println("Delta Aircraft: " + airCraft);
//Splitting the first word from the rest of the string
String arr[] = airCraft.split(" ", 2);
String firstWord = arr[0];
System.out.println(firstWord + " first class seat capacity: " + firstClass);
System.out.println(firstWord + " business class seat capacity: " + busiClass);
System.out.println(firstWord + " economy class seat capacity: " + econClass);
//Airline object
A8AirlineAircraftData airline = new A8AirlineAircraftData(airName, airCode, airCraft, firstClass, busiClass, econClass);
System.out.println(airName + " successfully added. Press Enter to continue.");
sc.nextLine();
sc.nextLine();//Press Enter to continue
return airline;
}
}
感谢您提供的任何指导。再一次，如果我不清楚或者我的提交在语法上不正确，我很抱歉。我试着简洁！
我现在将显示更改编辑：
public class A8AirlineAircraftData {
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + ((airCode == null) ? 0 : airCode.hashCode());
return result;
}
@Override
public boolean equals(Object obj) {
if (this == obj) {
return true;
}
if (!(obj instanceof A8AirlineAircraftData)) {
return false;
}
A8AirlineAircraftData other = (A8AirlineAircraftData) obj;
return Objects.equals(airCode, other.airCode);
}
private String airName; //these are all showing a warning saying 'Field ____ can be final'
private String airCode;
private String airCraft;
private int firstClass;
private int busiClass;
private int econClass;
//public String toStringAirLine(){return "airname is:" + airName + ", aircode is: "+airCode;}
public A8AirlineAircraftData(String airName, String airCode, String airCraft, int firstClass, int busiClass, int econClass) {
this.airName = airName;
this.airCode = airCode;
this.airCraft = airCraft;
this.firstClass = firstClass;
this.busiClass = busiClass;
this.econClass = econClass;
}
public static A8AirlineAircraftData AddAirline(Scanner sc) {
sc.nextLine();
System.out.println("Please enter the Airline name:");
String airName = sc.nextLine();
System.out.println("Please enter the Airline code:");
String airCode = sc.nextLine();
System.out.println("Please enter the Delta Aircraft:");
String airCraft = sc.nextLine();
System.out.println("Please enter the first class seat capacity:");
int firstClass = sc.nextInt();
System.out.println("Please enter the business class seat capacity:");
int busiClass = sc.nextInt();
System.out.println("Please enter the economy class seat capacity:");
int econClass = sc.nextInt();
System.out.println("Airline name: " + airName);
System.out.println("Airline code: " + airCode);
System.out.println("Delta Aircraft: " + airCraft);
//Splitting the first word from the rest of the string
String arr[] = airCraft.split(" ", 2);
String firstWord = arr[0];
System.out.println(firstWord + " first class seat capacity: " + firstClass);
System.out.println(firstWord + " business class seat capacity: " + busiClass);
System.out.println(firstWord + " economy class seat capacity: " + econClass);
//Airline object
A8AirlineAircraftData airline = new A8AirlineAircraftData(airName, airCode, airCraft, firstClass, busiClass, econClass);
Set<A8AirlineAircraftData> aircrafts = new HashSet<>();
/*for (int i = 0; i < 3; i++) {
aircrafts.add(A8AirlineAircraftData.AddAirline(sc));
} */
System.out.println(airName + " successfully added. Press Enter to continue.");
sc.nextLine();
sc.nextLine();//Press Enter to continue
return airline;
答案
您可以调用工厂方法并将创建的对象存储在Set中，例如。
例如，要创建3个元素，您可以编写：
Set<A8AirlineAircraftData> aircrafts = new HashSet<>();
for (int i=0; i<3; i++){
aircrafts.add(A8AirlineAircraftData.AddAirline());
}
我不允许任何重复的airCode，HashSet会以某种方式处理它吗？
Set中元素的唯一性依赖于它包含的equals() / hashCode()元素方法。
您应该在A8AirlineAircraftData中覆盖它们以依赖于以唯一方式标识实例的类字段：airCode。
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + ((airCode == null) ? 0 : airCode.hashCode());
return result;
}
@Override
public boolean equals(Object obj) {
if (this == obj)
return true;
if (!(obj instanceof A8AirlineAircraftData))
return false;
A8AirlineAircraftData other = (A8AirlineAircraftData) obj;
return Objects.equal(airCode, other.airCode);
}
另一答案
你是对的，Set是Set Objects实现的接口，它不允许重复。在您的代码中，airCode是一个String，因此不允许重复的字符串。要访问类外的变量或方法，必须为变量设置正确的访问修饰符。即公众将允许从任何其他类访问此变量。
public static Set<String> setOfAirCodes = new HashSet<>();
关于其他修饰语，请阅读：access modifiers in java
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