Java Scanner nextFloat() 方法

2024 年 11 月 6 日 | 阅读 2 分钟

Java Scanner 类的 nextFloat() 方法用于扫描下一个输入标记为 Float。如果翻译成功，扫描器将跳过已匹配的输入。

语法

以下是 nextFloat() 方法的声明

参数

此方法不接受任何参数。

返回值

nextFloat() 方法返回从输入扫描的 Float。

异常

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

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 ScannerNextFloatExample1 {  
    public static void main(String args[]){   	
    	int amount;
    	double balance;
    	//Insert amount and balance from console
    	Scanner input = new Scanner (System.in);
    	System.out.print("Enter the amount: ");
    	amount = input.nextInt();
    	System.out.print("Enter the Total Balance: ");
    	balance = input.nextFloat();
    	//Reduce amount+fee from balance
    	balance = balance-(amount + 0.50);
    	//Print new balance
    	System.out.print("New Balance is: "+balance);
      input.close();
	}  
}

输出

Enter the amount: 263426
Enter the Total Balance: 3434343.454
New Balance is: 3170917.0

示例 2

import java.util.*;
public class ScannerNextFloatExample2 {  
    public static void main(String args[]){   	
    	  float value;
        Scanner scan = new Scanner(System.in);     
        System.out.println("Input value : ");
        scan.close();
        value = scan.nextFloat();
        System.out.println("Float value : "+2.0*value );
	  }  
}

输出

Input value : 
Exception in thread "main" java.lang.IllegalStateException: Scanner closed
	at java.base/java.util.Scanner.ensureOpen(Scanner.java:1150)
	at java.base/java.util.Scanner.next(Scanner.java:1573)
	at java.base/java.util.Scanner.nextFloat(Scanner.java:2496)
	at myPackage.ScannerNextDoubleExample2.main(ScannerNextDoubleExample2.java:9)

示例 3

import java.util.*;  
public class ScannerNextFloatExample3 {  
     public static void main(String args[]){ 
    	   String str = "Hello World! 12 + 13.43 = 15.43 ";
         Float f = 2.123f;
         str = str + f;
         //Create scanner with string Object
         Scanner scanner = new Scanner(str);
         //Use US locale to be able to identify Float in the string
         scanner.useLocale(Locale.US);
         //Find the next float token and print it
         while (scanner.hasNext()) {
            //Check if the next is a float, print found
            if (scanner.hasNextFloat()) {
               System.out.println("Found Float: " + scanner.nextFloat());
            }
            //If float is not found, print "Not Found"
            System.out.println("Not Found Float: " + scanner.next());
         }    
         scanner.close();
     }  
} 

输出

Not Found Float: Hello
Not Found Float: World!
Found Float: 12.0
Not Found Float: +
Found Float: 13.43
Not Found Float: =
Found Float: 15.43
Not Found Float: 2.123

示例 4

import java.util.*;
public class ScannerNextFloatExample4 {  
    public static void main(String args[]){   	
    	  Float number;
        Scanner scan = new Scanner( System.in );     
        System.out.print("Enter the numeric value : ");
        number = scan.nextFloat();
        System.out.println("Float value : " + number +" \nTwice value : " + 2.0*number );
        scan.close();
	  }  
}

输出

Enter the numeric value : 74537453.56959
Float value : 7.4537456E7 
Twice value : 1.49074912E8

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Java Scanner nextFloat() 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 nextFloat() 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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