Java.util.Scanner.nextDouble() Java.util.Scanner.nextByte() Java.util.Scanner.nextFloat() 描述 所述java.util.Scanner.nextDouble()方法扫描输入作为双的下一个标记。如果下一个标记无法转换为有效的double值,则此方法将抛出InputMismatchException。如果翻译成功,扫描仪将超过匹配的输入。 声明 以下是java.util.Scanner.nextDouble()方法的声明 public double nextDouble() 参数 NA 返回值 此方法返回从输入扫描的双精度数 异常 InputMismatchException - 如果下一个标记与Float正则表达式不匹配,或者超出范围 NoSuchElementException - 如果输入已用尽 IllegalStateException - 如果此扫描程序已关闭 实例 以下示例显示了java.util.Scanner.nextDouble()方法的用法。 package com.tutorialspoint; import java.util.*; public class ScannerDemo { 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(); } } 让我们编译并运行上面的程序,这将产生以下结果 Not Found :Hello Not Found :World! Found :3.0 Not Found :+ Found :3.0 Not Found := Found :6.0 Not Found :true Java.util.Scanner.nextByte() Java.util.Scanner.nextFloat()