在不同的方法中插入不同的扫描程序时出现异常

Question

public static void main(String[] args) {
        Class2 cls = new Class2();
        cls.test();
    }

  public class Class2 {
 
        public Class2() {
        }
        
    public void test()
    {
        test2();
        test3();
        
    }
    
    public void test2() {
        Scanner scanner = new Scanner(System.in);
        System.out.println("give a String:");
        String str = scanner.next(); 
        scanner.close();
    }
    public void test3()
    {
        Scanner sc = new Scanner(System.in);
        System.out.println("give another String:");
        String str = sc.next();
        sc.close();
        
    }

}

Exception in thread "main" java.util.NoSuchElementException
    at java.base/java.util.Scanner.throwFor(Scanner.java:937)
    at java.base/java.util.Scanner.next(Scanner.java:1478)
    at Class2.test3(Class2.java:25)
    at Class2.test(Class2.java:11)
    at Class1.main(Class1.java:12)

我如何处理这个异常？通过在每种方法中保留一个不同的扫描器！

Answer 1

下面是您的经过修改的代码，并附有适当的注释。

class2.java

import java.util.Scanner;
public class Class2 {
    /*You dont have to create multiple scanner objects*/
    Scanner scan = new Scanner(System.in);

    public void test() {
        /*In order to run the methods in this class itself
        * you have to use static keyword or create object*/
        Class2 obj = new Class2();
        obj.test2();
        obj.test3();
        scan.close();
        /* As this method is run, scan.close() should be placed when you want to close InputStream
        * you will learn this in Java Streams*/
    }

    public void test2() {
        System.out.println("give a String:");
        String str = scan.nextLine();
    }
    public void test3() {
        System.out.println("give another String:");
        String str = scan.nextLine();

    }
}

Main.java

public class Main {
    public static void main(String[] args) {
        Class2 cls = new Class2();
        cls.test();
    }
}