Java Scanner nextDouble()方法

java.util.Scanner.nextDouble() 方法扫描输入的下一个标记为double。此方法将抛出InputMismatchException如果下一个标记不能转换为有效的double值。如果转换成功，则scanner执行匹配的输入。

1 语法

public double nextDouble()

2 参数

无

3 返回值

此方法返回从输入信息扫描的double值。

4 示例 

package com.yiidian;

/**
 * 一点教程网： http://www.yiidian.com
 */
/**
 * java.util.Scanner.nextDouble()方法的例子
 */
import java.util.*;

public class Demo {
    public static void main(String[] args) {

        String s = "Hello World! 3 + 3.0 = 6 true";

        // create a new scanner with the specified String Object
        Scanner scanner = new Scanner(s);

        // use US locale to be able to identify doubles in the string
        scanner.useLocale(Locale.US);

        // find the next double token and print it
        // loop for the whole scanner
        while (scanner.hasNext()) {

            // if the next is a double, print found and the double
            if (scanner.hasNextDouble()) {
                System.out.println("Found :" + scanner.nextDouble());
            }

            // if a double is not found, print "Not Found" and the token
            System.out.println("Not Found :" + scanner.next());
        }

        // close the scanner
        scanner.close();
    }
}

输出结果为：

Not Found :Hello
Not Found :World!
Found :3.0
Not Found :+
Found :3.0
Not Found :=
Found :6.0
Not Found :true