无法对基元类型int调用contains(int)

Question

我遇到了案例4的问题。我想用身份证找一个选民。它是公开的，上面写着Cannot invoke contains(int) on the primitive type int。为什么？Id实际上是公开的，但我不知道问题出在哪里。

我所要做的就是找到选民的身份证。

public class Voters {
public static HashSet<Voter> voters = new HashSet<>();
public static void main(String[] args) throws IOException {
while (true) {
System.out.println("1. Add New Voter");
System.out.println("2. List All Voters");
System.out.println("3. Find a Voter By Name");
System.out.println("4. Get information about specific voter");
System.out.println("5. Exit");
Scanner scanner = new Scanner(System.in);
int chosen = scanner.nextInt();
switch (chosen) {
case 1:
System.out.print("National ID Number: ");
int idNum = scanner.nextInt();
System.out.print("nName: ");
String name = scanner.next();
System.out.print("nMale Relative: ");
String maleRelative = scanner.next();
System.out.print("nAge: ");
int age = scanner.nextInt();
System.out.print("nAddress: ");
String address = scanner.next();
System.out.print("nProvince: ");
String province = scanner.next();
System.out.println("");
Voter voter = new Voter(idNum, name, maleRelative, age, address, province);
voters.add(voter);
FileWriter fileWriter = new FileWriter("C:\Users\YourPcName\Desktop\voters.txt");
fileWriter.append("n").append(voter.toString());
fileWriter.flush();
fileWriter.close();
break;
case 2:
for (Voter v : voters) {
System.out.println(v);
}
break;
case 3:
System.out.print("Name: ");
Scanner ss = new Scanner(System.in);
String n = ss.nextLine();
System.out.println();
for (Voter v : voters) {
if (v.name.contains(n)) {
System.out.println(v);
break;
}
}
break;
case 4:
System.out.print("Id: ");
Scanner nn = new Scanner(System.in);
int s = nn.nextInt();
System.out.println();
for (Voter v : voters) {
if (v.nationalIdNumber.contains(s)) {
System.out.println(v);
break;
}
}
break;
case 5:
System.exit(0);
break;
default:
}
}
}
static class Voter {
public int nationalIdNumber;
public String name;
public String maleRelativeName;
public int age;
public String address;
public String province;
public Voter(int nationalIdNumber, String name, String maleRelativeName, int age, String address,
String province) {
this.nationalIdNumber = nationalIdNumber;
this.name = name;
this.maleRelativeName = maleRelativeName;
this.age = age;
this.address = address;
this.province = province;
}
public String toString() {
return "Id: " + nationalIdNumber + "  Name: " + name + "  Male Relative: " + maleRelativeName + "  Age: "
+ age + "  Address: " + address + "  Province: " + province;
}
}

Answer 1

nationalIdNumber属于int类型，它没有任何方法。你想干什么？也许那行应该读

if (v.nationalIdNumber == s) {

我不知道。给我们更多的背景。