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()