教授要求我们制造一个可以进行基本计算的字符计算器。差不多完成了，但是我有一个问题要解决被零除的问题。每个人都知道一个数字不能除以零。如果我问用户两个浮点数，而他给我的第二个浮点数是0，该怎么办？我知道它应该在division（）下，并且我已经尝试了很多次使用if语句，但无法正常工作。如果用户做错了，我该写些什么让用户有第二次机会重写两个浮点数，并告诉他第二个数字不应为零。如果用户首先输入错误，那么我编写的程序只会给出错误的答案。有人可以帮我吗？
import java.util.Scanner;
public class Calculator {
static Scanner scan;
public static void main(String[] args) {
String choice = "";
scan = new Scanner(System.in);
while(true) {
System.out.println("Welcome to <'s> Handy Calculator\n"+"\n\t1. Addition\n\t2. Subtraction\n\t3. Multiplication\n\t4. Division\n\t5. Exit\n");
System.out.println("What would you like to do? ");
choice=scan.nextLine();
if (choice.equals("1")) {
if(!addition()){
System.out.println("\nYou have entered invalid input. Please try again");
}
System.out.println("\nPress enter key to continue...");
scan.nextLine();
}
else if(choice.equals("2")){
if(!subtraction()){
System.out.println("\nYou have entered invalid input. Please try again");
}
System.out.println("\nPress enter key to continue...");
scan.nextLine();
}
else if(choice.equals("3")){
if(!multiplication()){
System.out.println("\nYou have entered invalid input. Please try again");
}
System.out.println("\nPress enter key to continue...");
scan.nextLine();
}
else if(choice.equals("4")){
if(!division()){
System.out.println("\nYou have entered invalid input. Please try again");
}
System.out.println("\nPress enter key to continue...");
scan.nextLine();
}
else if(choice.equals("5")){
System.out.println("\nThank you for using <'s> Handy Calculator");
break;
}
else{
System.out.println("\nInvalid input. Please input an integer between 1 and 5\n");
continue;
}
}
}
private static boolean addition() {
System.out.println("\nPlease enter two floats to add, separated by a space: ");
String input = scan.nextLine();
try{
Float f1 = Float.parseFloat(input.split(" ")[0]);
Float f2 = Float.parseFloat(input.split(" ")[1]);
System.out.println("\nResult of adding "+f1+" and "+f2+" is: "+(f1+f2));
}
catch(Exception e){
return false;
}
return true;
}
private static boolean subtraction() {
System.out.println("\nPlease enter two floats to subtract, separated by a space: ");
String input = scan.nextLine();
try{
Float f1 = Float.parseFloat(input.split(" ")[0]);
Float f2 = Float.parseFloat(input.split(" ")[1]);
System.out.println("\nResult of subtract "+f2+" from "+f1+" is: "+(f1-f2));
}
catch(Exception e){
return false;
}
return true;
}
private static boolean multiplication() {
System.out.println("\nPlease enter two floats to multiply, separated by a space: ");
String input = scan.nextLine();
try{
Float f1 = Float.parseFloat(input.split(" ")[0]);
Float f2 = Float.parseFloat(input.split(" ")[1]);
System.out.println("\nResult of multiply "+f1+" and "+f2+" is: "+(f1*f2));
}
catch(Exception e){
return false;
}
return true;
}
private static boolean division() {
System.out.println("\nPlease enter two floats to divide, separated by a space: ");
String input = scan.nextLine();
try{
Float f1 = Float.parseFloat(input.split(" ")[0]);
Float f2 = Float.parseFloat(input.split(" ")[1]);
if(f2==0) {
System.out.println("the second number should not be zero, please do agian");
scan.nextLine();
}
System.out.println("\nResult of dividing "+f1+" by "+f2+" is: "+(f1/f2));
}
catch(Exception e){
return false;
}
return true;
}
}
答案 0 :(得分：0)
我该写些什么让用户有第二次重写两次的机会 如果他做错了，就会浮动，并告诉他第二个数字不应该 为零？如果用户将我编写的程序给出错误的答案， 首先输入错误。
您需要一个while循环。我已经测试过了，这可以解决问题：
private static boolean division() {
System.out.println("\nPlease enter two floats to divide, separated by a space: ");
String input = scan.nextLine();
Float f1 = 0.0f;
Float f2 = 0.0f;
boolean validInput = false;
while (!validInput) {
f1 = Float.parseFloat(input.split(" ")[0]);
f2 = Float.parseFloat(input.split(" ")[1]);
if (f2 == 0) {
System.out.println("the second number should not be zero, please do agian");
input = scan.nextLine();
} else {
validInput = true;
}
}
System.out.println("\nResult of dividing " + f1 + " by " + f2 + " is: " + (f1 / f2));
return true;
}
并且您不需要try/catch-代码永远不会从头开始抛出异常。
答案 1 :(得分：0)
您必须在循环中检查输入float是否等于0，如果输入等于System.out.println("\nPlease enter two floats to divide, separated by a space:");
float f1 = scan.nextFloat();
float f2 = scan.nextFloat();
while (Float.compare(f2, 0) == 0) {
System.out.println("the second number should not be zero, please do agian");
f2 = scan.nextFloat();
}
return String.format(LOCALE, "\n%.2f / %.2f = %.2f", f1, f2, f1 / f2);
，请取消输入。
public final class Calculator {
private static final String TITLE = "<'s> Handy Calculator";
private static final Locale LOCALE = Locale.US;
private static final char EXIT = '0';
private static void proceed(Scanner scan) {
while (true) {
try {
System.out.println("Welcome to " + TITLE + '\n');
Stream.of(Operation.values())
.filter(op -> Objects.nonNull(op.title))
.forEach(op -> System.out.format("\t%s. %s\n", op.id, op.title));
System.out.println("\t" + EXIT + ". Exit\n");
System.out.println("What would you like to do? ");
char choice = scan.next().charAt(0);
if (choice == EXIT) {
System.out.println("\nThank you for using " + TITLE);
return;
}
System.out.println(Operation.parseId(choice).apply(scan));
System.out.println();
} catch(Exception e) {
System.err.println("\nYou have entered invalid input. Please try again");
} finally {
System.out.println("\nPress enter key to continue...");
scan.nextLine();
}
}
}
private enum Operation implements Function<Scanner, String> {
UNKNOWN('\0', null) {
@Override
public String apply(Scanner scan) {
return "\nInvalid input. Please input an integer between 1 and 5";
}
},
ADDITION('1', "Addition") {
@Override
public String apply(Scanner scan) {
System.out.println("\nPlease enter two floats to add, separated by a space:");
float f1 = scan.nextFloat();
float f2 = scan.nextFloat();
return String.format(LOCALE, "\n%.2f + %.2f = %.2f", f1, f2, f1 + f2);
}
},
SUBTRACTION('2', "Subtraction") {
@Override
public String apply(Scanner scan) {
System.out.println("\nPlease enter two floats to subtract, separated by a space:");
float f1 = scan.nextFloat();
float f2 = scan.nextFloat();
return String.format(LOCALE, "\n%.2f - %.2f = %.2f", f1, f2, f1 - f2);
}
},
MULTIPLICATION('3', "Multiplication") {
@Override
public String apply(Scanner scan) {
System.out.println("\nPlease enter two floats to multiply, separated by a space:");
float f1 = scan.nextFloat();
float f2 = scan.nextFloat();
return String.format(LOCALE, "\n%.2f * %.2f = %.2f", f1, f2, f1 * f2);
}
},
DIVISION('4', "Division") {
@Override
public String apply(Scanner scan) {
System.out.println("\nPlease enter two floats to divide, separated by a space:");
float f1 = scan.nextFloat();
float f2 = scan.nextFloat();
while (Float.compare(f2, 0) == 0) {
System.out.println("the second number should not be zero, please do agian");
f2 = scan.nextFloat();
}
return String.format(LOCALE, "\n%.2f / %.2f = %.2f", f1, f2, f1 / f2);
}
};
private final char id;
private final String title;
Operation(char id, String title) {
this.id = id;
this.title = title;
}
public static Operation parseId(char id) {
for (Operation operation : values())
if (id == operation.id)
return operation;
return UNKNOWN;
}
}
public static void main(String... args) {
try (Scanner scan = new Scanner(System.in)) {
scan.useLocale(LOCALE);
proceed(scan);
}
}
}
下面，我对您的代码进行了重构。希望您能更清楚地了解它。
from typing import List
def find_smallest(arr:List) -> int:
smallest = arr[0] #set pivot
smallest_index = 0
for i in range(1, len(arr)):
if arr[i] < smallest:
smallest = arr[i]
smallest_index = i
return smallest_index
def selection_sort(arr) -> List:
new_arr = []
for i in range(len(arr)):
smallest = find_smallest(arr)
new_arr.append(arr.pop(smallest))
return new_arr