英文:
How to implement discretionary use of Scanner
问题
我是Java的新手，所以如果这显得很简单，我提前道歉。但是，我有一个简单的计算器，按照每个物品“a”的价格为每个物品“b”美元打印成本，但是如果你有超过“c”的物品，那么它的成本是“d”美元。对应的代码如下：
Scanner sc = new Scanner(System.in);int a = sc.nextInt(), b = sc.nextInt(), c = sc.nextInt(), d = sc.nextInt();if (a < b){System.out.printf("%d", a * c);}if (a == b){System.out.printf("%d", a * c);}if (a > b){System.out.printf("%d", a * d);}
但我想增加一些灵活性并避免歧义，也就是说，用户输入类似 a=10 b=5 c=4 d=10 或 b=5 d=10 a=10 c=4（或任何组合），都在一行上进行，输出都为 100。因此，我的问题是，如何使用户输入变量的顺序是任意的，同时保持相同的功能？
谢谢。
英文:
I'm a Java newbie, so I apologize in advance if this is trivial. But, I have a simple calculator that prints the cost of 'a' items by 'b' dollars, but if you have more than 'c' items, then it costs 'd' dollars. The code for that is:
Scanner sc = new Scanner(System.in);int a = sc.nextInt(), b = sc.nextInt(), c = sc.nextInt(), d = sc.nextInt();if (a < b){System.out.printf("%d", a * c);}if (a == b){System.out.printf("%d", a * c);}if (a > b){System.out.printf("%d", a * d);}
but I'd like to add a bit more flexibility and avoid ambiguity, that is, the user inputs something like a=10 b=5 c=4 d=10 or b=5 d=10 a=10 c=4 (or any combination) all on one line, and the output is 100 for both. So, my question is how can I make it so that the order in which the user inputs the variables is arbitrary, all whilst keeping the same functionality?
TIA
答案1
得分: 1
你可以按照以下方式进行操作：
import java.util.HashMap;import java.util.Map;import java.util.Scanner;public class Main {public static void main(String[] args) {Scanner scanner = new Scanner(System.in);System.out.println("输入数值：");String input = scanner.nextLine(); // 扫描整行输入// 使用空白字符拆分输入String[] parts = input.split("\\s+");// 创建一个带有部分的映射Map<String, Integer> map = new HashMap<>();for (String part : parts) {// 在'='处拆分String[] tokens = part.split("=");map.put(tokens[0], Integer.valueOf(tokens[1]));}// 下面的处理与您已经在做的类似if (map.get("a") < map.get("b")) {System.out.printf("%d", map.get("a") * map.get("c"));}if (map.get("a") == map.get("b")) {System.out.printf("%d", map.get("a") * map.get("c"));}if (map.get("a") > map.get("b")) {System.out.printf("%d", map.get("a") * map.get("d"));}}}
示例运行:
输入数值：a=10 b=5 c=4 d=10100
另一个示例运行:
输入数值：b=5 d=10 a=10 c=4100
注意: 这个解决方案是为了引导您的进展。还有很多工作要做（例如验证、异常处理等），以使其更好。
英文:
You can do something like as follows:
import java.util.HashMap;import java.util.Map;import java.util.Scanner;public class Main {public static void main(String[] args) {Scanner scannner = new Scanner(System.in);System.out.println("Enter the values: ");String input = scannner.nextLine();// Scan the complete line// Split the input on whitespaceString[] parts = input.split("\\s+");// Create a Map with partsMap<String, Integer> map = new HashMap<>();for (String part : parts) {// Split on '='String[] tokens = part.split("=");map.put(tokens[0], Integer.valueOf(tokens[1]));}// The following processing is similar to what you are already doingif (map.get("a") < map.get("b")) {System.out.printf("%d", map.get("a") * map.get("c"));}if (map.get("a") == map.get("b")) {System.out.printf("%d", map.get("a") * map.get("c"));}if (map.get("a") > map.get("b")) {System.out.printf("%d", map.get("a") * map.get("d"));}}}
A sample run:
Enter the values:a=10 b=5 c=4 d=10100
Another sample run:
Enter the values:b=5 d=10 a=10 c=4100
Note: This solution is to guide you progress. There is a lot to be done (e.g. validations, exception handling etc.) in order to make it better.
答案2
得分: 1
尝试这个：import java.util.Scanner;public class SimpleCalculatorScanner {public static void main(final String[] args) {Scanner sc = new Scanner(System.in);String[] variables = sc.nextLine().split(" ");int a = 0;int b = 0;int c = 0;int d = 0;for(int i = 0; i < variables.length; i++) {try {if(variables[i].substring(0, 2).equals("a=")) {a=Integer.parseInt(variables[i].substring(2));}else if(variables[i].substring(0, 2).equals("b=")) {b=Integer.parseInt(variables[i].substring(2));}else if(variables[i].substring(0, 2).equals("c=")) {c=Integer.parseInt(variables[i].substring(2));}else if(variables[i].substring(0, 2).equals("d=")){d=Integer.parseInt(variables[i].substring(2));}else {System.out.println("无法识别的变量 "+variables[i].substring(0, 1)+" 检测到");return;}}catch(NumberFormatException e) {System.out.println("你分配给变量 "+variables[i].substring(0, 1)+" 的字符不是一个数字");return;}}if (a < b){System.out.printf("%d", a * c);}if (a == b){System.out.printf("%d", a * c);}if (a > b){System.out.printf("%d", a * d);}}}**示例输入/输出***输入*b=5 d=10 a=10 c=4*输出*100*输入 2*b=5 d=10 e=10 c=4**输出 2**无法识别的变量 e 检测到*输入 3*a=10 b=5 c=4 d=iforgot*输出 3*你分配给变量 d 的字符不是一个数字**工作原理**Scanner读取一行，然后通过分割每个空格将其转换为数组。一旦变量被存储到数组中，我们运行一个**for**循环来测试数组中每个项的前两个字符是否为`a=`、`b=`、`c=`或`d=`。如果是`a=`，则将`=`后的每个字符解析为整数，并将其赋值给变量a，依此类推。如果它无法识别变量，它将打印出`无法识别的变量 <variablename> 检测到`。如果分配给变量的字符不是数字，它将打印出`你分配给变量 <variablename> 的字符不是一个数字`。
英文:
Try this:
import java.util.Scanner;public class SimpleCalculatorScanner {public static void main(final String[] args) {Scanner sc = new Scanner(System.in);String[] variables = sc.nextLine().split(" ");int a = 0;int b = 0;int c = 0;int d = 0;for(int i = 0; i < variables.length; i++) {try {if(variables[i].substring(0, 2).equals("a=")) {a=Integer.parseInt(variables[i].substring(2));}else if(variables[i].substring(0, 2).equals("b=")) {b=Integer.parseInt(variables[i].substring(2));}else if(variables[i].substring(0, 2).equals("c=")) {c=Integer.parseInt(variables[i].substring(2));}else if(variables[i].substring(0, 2).equals("d=")){d=Integer.parseInt(variables[i].substring(2));}else {System.out.println("Unrecognized variable "+variables[i].substring(0, 1)+" detected");return;}}catch(NumberFormatException e) {System.out.println("The character you assigned to variable "+variables[i].substring(0, 1)+" isn't a number");return;} }if (a < b){System.out.printf("%d", a * c);}if (a == b){System.out.printf("%d", a * c);}if (a > b){System.out.printf("%d", a * d);}}}
Sample I/O
Input
b=5 d=10 a=10 c=4
Output
100
Input 2
b=5 d=10 e=10 c=4
Output 2
Unrecognized variable e detected
Input 3
a=10 b=5 c=4 d=iforgot
Output 3
The character you assigned to variable d isn't a number
How it works
The Scanner reads a new line, and then turns it into an array by splitting every space.
Once the variables have been stored into an array, we run a for loop to test whether the first 2 characters of each item of the array are a=, b=, c= or d=. If it is a=, then it parses the every character after the = of the item in the array into an integer, and assigns it to variable a, vice versa.
If it doesn't recognize the variable, it will print Unrecognized variable <variablename> detected.
If the character assigned to the variable wasn't a number, it will print The character you assigned to variable <variablename> isn't a number
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