Java Scanner hasNextBoolean()方法及示例

java.util.Scanner 类的 hasNextBoolean() 方法，如果该扫描器输入的下一个标记可以用nextBoolean()方法解释为一个布尔值，则返回true。该扫描器不会超过任何输入。

语法

public boolean hasNextBoolean()

参数： 该函数不接受任何参数。

返回值 ：当且仅当这个扫描器的下一个标记是一个有效的布尔值时，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// hasNextBoolean() 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 true geeks!";          // new scanner with the        // specified String Object        Scanner scanner = new Scanner(s);          // use US locale to interpret Booleans in a string        scanner.useLocale(Locale.US);          // iterate till end        while (scanner.hasNext()) {              // check if the scanner's            // next token is a Boolean with the default radix            System.out.print("" + scanner.hasNextBoolean());              // print what is scanned            System.out.print(" -> " + scanner.next() + "\n");        }          // close the scanner        scanner.close();    }}

输出:

false -> gfgtrue -> truefalse -> geeks!

程序2： 展示例外情况的计划

// Java program to illustrate the// hasNextBoolean() method of Scanner class in Java// Exception case  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 Booleans in a string            scanner.useLocale(Locale.US);              scanner.close();              // iterate till end            while (scanner.hasNext()) {                  // check if the scanner's                // next token is a Boolean with the default radix                System.out.print("" + scanner.hasNextBoolean());                  // print what is scanned                System.out.print(" -> " + scanner.next() + "\n");            }              // close the scanner            scanner.close();        }        catch (IllegalStateException e) {            System.out.println("Exception: " + e);        }    }}

输出:

Exception: java.lang.IllegalStateException: Scanner closed

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