java 异常 exception in thread main java.util.nosuchelementexception: no line found-ag捕鱼王app官网

本篇文章介绍如何解决java中的异常 exception in thread "main" java.util.nosuchelementexception: no line found。

java 异常 exception in thread "main" java.util.nosuchelementexception: no line found

java.util.nosuchelementexception 是运行时未经检查的异常。 当我们使用 next()、nextelement()、迭代器、方法或枚举等方法时，jvm 会引发此异常。

当我们使用扫描仪通过 nextline(); 等方法获取用户输入时，会出现错误 exception in thread "main" java.util.nosuchelementexception: no line found 。 当我们尝试使用没有任何边界的方法时，就会发生错误。

让我们尝试一个演示此错误的示例。

package jiyik;
import java.util.scanner;
public class example {
    static boolean[][] articles;
    public static void main(string[] args) {
        // this initiates all array values to be false
        articles = new boolean[4][4];
        for (int i = 0; i < 4; i  ) {
                for (int j = 0; j < 4; j  ) {
                    articles[i][j] = false;
                }
               // welcome message
                system.out.println("-------------------------");
                system.out.println("welcome to jiyik.com.");
                system.out.println("-------------------------\n");
               // starts program
               programstart();
        }
    }
    public static void programstart() {
      // to read users' input
       scanner sc = new scanner(system.in);
       //user input
        string requested_lanuguage;
        string requested_article;
        // counters for articles array
        int count_language = 0;
        int count_artciles = 0;
        // user to select their choice of programming language
        system.out.print("please type 1 for java or 2 for python: ");
        // language preference
        requested_lanuguage = sc.nextline();
        switch (requested_lanuguage) {
            case "1":
                // user selects java
                system.out.println(">>> you have selected java. \n");
                break;
            case "2":
                // user selects python
                system.out.println(">>> you have selected python. \n");
                break;
            default:
                // user has not selected a valid programming language
                system.out.println(">>> you have not selected a valid choice. please try again. \n");
                programstart();
                break;
        }
       // user to select their choice of article
       system.out.print("please type 1 for web and 2 for app: ");
       // article preference
       requested_article = sc.nextline();
       switch (requested_article) {
           case "1":
               // user selects web articles
               system.out.println(">>> you have selected web articles. \n");
               break;
           case "2":
               // user selects app articles
               system.out.println(">>> you have selected app articles. \n");
               break;
           default:
                // user has not selected a valid article
                system.out.println(">>> you have not selected a choice. please try again. \n");
                programstart();
                break;
            }
        // closes scanner
       sc.close();
    }
}

上面代码的输出是：

-------------------------
welcome to jiyik.com.
-------------------------
please type 1 for java or 2 for python: 1
>>> you have selected java.
please type 1 for web and 2 for app: 1
>>> you have selected web articles.
exception in thread "main" -------------------------
welcome to jiyik.com.
-------------------------
please type 1 for java or 2 for python: java.util.nosuchelementexception: no line found
    at java.base/java.util.scanner.nextline(scanner.java:1651)
    at jiyik.example.programstart(example.java:45)
    at jiyik.example.main(example.java:24)

发生错误是因为我们使用没有任何边界的方法 nextline() 。 为了解决这个问题，我们需要替换代码 requested_article = sc.nextline(); 到以下代码。

while(sc.hasnextline()){
    requested_article = sc.nextline();
    // switch condition here
}

让我们尝试一下ag捕鱼王app官网的解决方案。

package jiyik;
import java.util.scanner;
public class example {
    static boolean[][] articles;
    public static void main(string[] args) {
        // this initiates all array values to be false
        articles = new boolean[4][4];
        for (int i = 0; i < 4; i  ) {
                for (int j = 0; j < 4; j  ) {
                    articles[i][j] = false;
                }
               // welcome message
                system.out.println("-------------------------");
                system.out.println("welcome to jiyik.com.");
                system.out.println("-------------------------\n");
               // starts program
               programstart();
        }
    }
    public static void programstart() {
        // to read users' input
        scanner sc = new scanner(system.in);
        //user input
        string requested_lanuguage;
        string requested_article;
        // counters for articles array
        int count_language = 0;
        int count_artciles = 0;
        // user to select their choice of programming language
        system.out.print("please type 1 for java or 2 for python: ");
        // language preference
        requested_lanuguage = sc.nextline();
        switch (requested_lanuguage) {
            case "1":
                // user selects java
                system.out.println(">>> you have selected java. \n");
                break;
            case "2":
                // user selects python
                system.out.println(">>> you have selected python. \n");
                break;
            default:
                // user has not selected a valid programming language
                system.out.println(">>> you have not selected a valid choice. please try again. \n");
                programstart();
                break;
        }
       // user to select their choice of article
       system.out.print("please type 1 for web and 2 for app: ");
       // article preference
       while(sc.hasnextline()){
            requested_article = sc.nextline();
       switch (requested_article) {
           case "1":
               // user selects web articles
               system.out.println(">>> you have selected web articles. \n");
               break;
           case "2":
               // user selects app articles
               system.out.println(">>> you have selected app articles. \n");
               break;
           default:
                // user has not selected a valid article
                system.out.println(">>> you have not selected a choice. please try again. \n");
                programstart();
                break;
            }
        }
        // closes scanner
       sc.close();
    }
}

上面的代码不会抛出 exception in thread "main" java.util.nosuchelementexception: no line found now。 查看输出：

-------------------------
welcome to jiyik.com.
-------------------------
please type 1 for java or 2 for python: 1
>>> you have selected java.
please type 1 for web and 2 for app: 1
>>> you have selected web articles.
1
>>> you have selected web articles.
>>> you have not selected a choice. please try again.
please type 1 for java or 2 for python: