Java Scanner hasNextLine()方法及示例

java.util.Scanner 类的 hasNextLine() 方法如果在该扫描器的输入中存在另一行，则返回true。该方法在等待输入时可能会阻塞。扫描器不会因为任何输入而前进。

语法

public boolean hasNextLine()

参数： 该函数不接受任何参数。

返回值： 当且仅当该扫描器有另一行输入时，该函数返回真。

异常 ：如果这个扫描器被关闭，该函数会抛出IllegalStateException。

下面的程序说明了上述函数。

程序1 :

// Java program to illustrate the
// hasNextLine() method of Scanner class in Java
// without parameter
  
import java.util.*;
  
public class GFG1 {
    public static void main(String[] argv)
        throws Exception
    {
  
        String s = "gfg 2 geeks!";
  
        // new scanner with the
        // specified String Object
        Scanner scanner = new Scanner(s);
  
        // use US locale to interpret Lines in a string
        scanner.useLocale(Locale.US);
  
        // iterate till end
        while (scanner.hasNextLine()) {
  
            // print what is scanned
            System.out.println(scanner.nextLine());
        }
  
        // close the scanner
        scanner.close();
    }
}

输出:

gfg 2 geeks!

程序2： 展示例外情况的计划

// Java program to illustrate the
// hasNextLine() method of Scanner class in Java
// without parameter
  
import java.util.*;
  
public class GFG1 {
    public static void main(String[] argv)
        throws Exception
    {
        try {
  
            String s = "gfg 2 geeks!";
  
            // new scanner with the
            // specified String Object
            Scanner scanner = new Scanner(s);
  
            // use US locale to interpret Lines in a string
            scanner.useLocale(Locale.US);
  
            scanner.close();
  
            // iterate till end
            while (scanner.hasNextLine()) {
  
                // print what is scanned
                System.out.println(scanner.nextLine());
            }
  
            // close the scanner
            scanner.close();
        }
        catch (IllegalStateException e) {
            System.out.println("Exception is: " + e);
        }
    }
}

输出:

Exception is: java.lang.IllegalStateException: Scanner closed

**参考资料: ** https://docs.oracle.com/javase/7/docs/api/java/util/Scanner.html#hasNextLine()