Java Scanner nextDouble() 方法

2024 年 11 月 6 日 | 阅读 2 分钟

nextDouble() 是 Java Scanner 类的一个方法，用于将下一个输入标记扫描为 double 类型。如果转换成功，则扫描器会跳过已匹配的输入。

语法

以下是 nextDouble() 方法的声明

参数

此方法不接受任何参数。

返回值

nextDouble() 方法返回扫描的 double 类型输入。

异常

InputMismatchException - 如果下一个标记不匹配 Float 正则表达式或超出范围，则会抛出此异常。

NoSuchElementException - 如果输入耗尽，将抛出此异常。

IllegalStateException - 如果在 Scanner 关闭后调用，则会抛出此异常。

兼容版本

Java 1.5 及以上版本

示例 1

import java.util.*;
public class ScannerNextDoubleExample1 {  
    public static void main(String args[]){   	
    	  int amount;
        double balance;
        //Insert amount and balance from console
        Scanner input = new Scanner (System.in);
        System.out.println("Enter the amount: ");
        amount = input.nextInt();
        System.out.println("Enter the Total Balance: ");
        balance = input.nextDouble();
        //reduce amount+fee from balance
        balance=balance-(amount + 0.50);
        //print new balance
        System.out.print("Left Balance is: "+balance);
        input.close();
	    }  
}

输出

Enter the amount: 
213734
Enter the Total Balance: 
5684566.856
Left Balance is: 5470832.356

示例 2

import java.util.*;  
public class ScannerNextDoubleExample2 {  
     public static void main(String args[]){ 
    	   String str = "Hello World! 12 + 13.0 = 15 ";
         Float f = 2.123f;
         str = str + f;
         //Create a new scanner with string Object
         Scanner scanner = new Scanner(str);
         //Use US locale to be able to identify doubles in the string
         scanner.useLocale(Locale.US);
         //Find the next double token and print it
         while (scanner.hasNext()) {
            //Check if the next is a double, print found
            if (scanner.hasNextDouble()) {
               System.out.println("Found Double:" + scanner.nextDouble());
            }
            //If double is not found, print "Not Found"
            System.out.println("Not Found Double:" + scanner.next());
         }    
         scanner.close();
     }  
} 

输出

Not Found Double:Hello
Not Found Double:World!
Found Double:12.0
Not Found Double:+
Found Double:13.0
Not Found Double:=
Found Double:15.0
Not Found Double:2.123

示例 3

import java.util.*;
public class ScannerNextDoubleExample3 {  
    public static void main(String args[]){   	
    	    Scanner scan = new Scanner(System.in);
    	    System.out.print("Enter value: ");  	    
    	    if(scan.hasNextDouble())
    	    {
    	      double y  = scan.nextDouble();
    	      System.out.println("Your entered Double value: " +y);
    	    }   	            
    	    else if (scan.hasNext())
    	    {
    	    	System.out.println("Please Entered the Double Value.");
    	      System.out.println("You entered: " + scan.next());
    	    }
    	    scan.close()
	    }  
}

输出

Enter value: 375437.565
Your entered Double value: 375437.565

示例 4

import java.util.*;
public class ScannerNextDoubleExample4 {  
    public static void main(String args[]){   	
    	  double value;
        Scanner scan = new Scanner(System.in);     
        System.out.print("Enter the numeric value : ");
        value = scan.nextDouble();
        System.out.println("Double value : " + value +" \nTwice value : " + 2.0*value );
        scan.close();
	  }  
}

输出

Enter the numeric value : 12345
Double value : 12345.0 
Twice value : 24690.0

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Java Scanner nextDouble() 方法

语法

参数

返回值

异常

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示例 3

示例 4

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Java Scanner nextDouble() 方法

语法

参数

返回值

异常

兼容版本

示例 1

示例 2

示例 3

示例 4

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