java - 如果选择相同则扫描仪

Question

如果选择相同，我需要扫描仪才能使用，但这不起作用，有什么建议来修复它吗？

我需要它，所以当输入等于 32、64、128 或 356 时，它将输出相关行，但是当我运行代码时，我才得到这个，错误:(18, 18)java找不到符号符号:变量等于location:java.lang.string类型的变量选择

    package com.company;
import java.util.Scanner;
import java.util.Random;
public class Main {
    public static final String ALPHA_CHARS = "0123456789abcdefghijklmnopqrstuvwxyz";
    static Scanner scan = new Scanner(System.in);
    private static String getNum() {
        Random r = new Random();
        int offset = r.nextInt(ALPHA_CHARS.length());
        return ALPHA_CHARS.substring(offset, offset+1);
    }
public static int Length = 0;
    public static void main(String[] args) {
    System.out.println("Choose the Strings length, It must be either 32, 64, 128 or 256 characters.");
    System.out.println("Enter a value.");
    String choice;
    choice = scan.nextLine();
    if(choice.equals == 32) {
        System.out.println("Generating 32 Characters.");
        System.out.println(getNum());
    }
    if(choice.equals == 64) {
        System.out.println("Generating 64 Characters.");
    }
    if(choice.equals == 128) {
        System.out.println("Generating 128 Characters.");
    }
    if(choice.equals == 256) {
        System.out.println("Generating 256 Characters.");
    }
    else {
        System.out.println("Choose a valid integer.");
    }
    }
}

Answer 1

您正在扫描String并将其与int进行比较。此外，在这种情况下最好使用else if:

public static final String ALPHA_CHARS = "0123456789abcdefghijklmnopqrstuvwxyz";
static Scanner scan = new Scanner(System.in);
private static String getNum() {
    Random r = new Random();
    int offset = r.nextInt(ALPHA_CHARS.length());
    return ALPHA_CHARS.substring(offset, offset+1);
}

public static int Length = 0;
public static void main(String[] args) {
    System.out.println("Choose the Strings length, It must be either 32, 64, 128 or 256 characters.");
    System.out.println("Enter a value.");
    int choice;
    choice = scan.nextInt();
    if(choice == 32) {
        System.out.println("Generating 32 Characters.");
        System.out.println(getNum());
    }else if(choice == 64) {
        System.out.println("Generating 64 Characters.");
    }else if(choice == 128) {
        System.out.println("Generating 128 Characters.");
    }else if(choice == 256) {
        System.out.println("Generating 256 Characters.");
    }else {
        System.out.println("Choose a valid integer.");
    }
}