Java Scanner hasNextDouble()用法及代码示例

如果可以使用nextDouble()方法将此扫描仪输入中的下一个标记解释为Double，则java.util.Scanner类的hasNextDouble()方法将返回true。扫描仪不会越过任何输入。

用法:

public Double hasNextDouble()

参数：该函数不接受任何参数。

返回值：仅当此扫描仪的下一个令牌为有效Double时，此函数才返回true。

异常注意：如果关闭此扫描器，则此函数将引发IllegalStateException。

以下示例程序旨在说明上述函数：

示例1:

// Java program to illustrate the 
// hasNextDouble() 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 Doubles in a string 
        scanner.useLocale(Locale.US); 
  
        // iterate till end 
        while (scanner.hasNext()) { 
  
            // check if the scanner's 
            // next token is a Double with the default radix 
            System.out.print("" + scanner.hasNextDouble()); 
  
            // print what is scanned 
            System.out.print(" -> " + scanner.next() + "\n"); 
        } 
  
        // close the scanner 
        scanner.close(); 
    } 
}

输出：

false -> gfg
true -> 2
false -> geeks!

示例2:演示异常的程序

// Java program to illustrate the 
// hasNextDouble() 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 Doubles in a string 
            scanner.useLocale(Locale.US); 
  
            scanner.close(); 
  
            // iterate till end 
            while (scanner.hasNext()) { 
  
                // check if the scanner's 
                // next token is a Double with the default radix 
                System.out.print("" + scanner.hasNextDouble()); 
  
                // 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： https://docs.oracle.com/javase/7/docs/api/java/util/Scanner.html#hasNextDouble()

相关用法

注：本文由纯净天空筛选整理自gopaldave大神的英文原创作品 Scanner hasNextDouble() method in Java with Examples。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。