Java初学者编程，将字符串放入char数组以过滤输入

Question

in this code I've been trying to filter the characters in the array with a for-loop to a second array, but am unable to. Could anyone tell me what is exactly wrong with my code?

public class Deel1 {

    public static void main(String[] args) {
        String zinInvoer = getInput();
        String zinUitvoer = filterZin(zinInvoer);
    }

    static String getInput() {
        Scanner scan = new Scanner(System.in);
        String zinInvoer = "";

        System.out.println("Voer een zin in: ");
        if (scan.hasNextLine()) {
            zinInvoer = scan.nextLine().trim();
        }

        if (zinInvoer.equals("")) {
            System.out.println("Geen invoer!");
            System.exit(0);
        }
        return zinInvoer;
    }

    static String filterZin(String zinInvoer) {
        String zinUitvoer = "";
        char ongefilterd[] = zinInvoer.toCharArray();
        String nogFilteren = new String(ongefilterd);
        char a = nogFilteren.charAt(97);
        for (a = 97; a <= 122; a++) {
            a = a += 32;  
            char gefilterd[] = //second array to be printed
        }
        System.out.println("Gefilterd: " + zinUitvoer);
        return zinInvoer;
    }
}

Answer 1

Sorry if it annoys you but I had to translate your variables into english in order to figure out what their purposes were.

First of all, it will always throw an exception when the string is less than 98 letters long because it looks for the 97th letter. Second, the for loop in "filterZin" will only filter letter # 98, which I am guessing was not your intention. Also, geFilterd should probably be created outside of the for loop, and in the for loop you (i guess) would want to do

geFilterd[a]=a+32;
a+=32;

Because I couldn't figure out what your overall goal was for this program, I made a version of it that does what I think you were trying to do, but again, I do not know.

import java.util.Scanner;

public class Deel1 {

public static void main(String[] args) {
    String phraseInput = getInput();
    filterPhrase(phraseInput);
}

static String getInput() {
    Scanner scan = new Scanner(System.in);
    String phraseInput = "";

    System.out.println("Voer een zin in: ");
    if (scan.hasNextLine()) {
        phraseInput = scan.nextLine().trim();
    }

    if (phraseInput.equals("")) {
        System.out.println("Geen invoer!");
        System.exit(0);
    }
    return phraseInput;
}

static String filterPhrase(String phraseInput) {
    String phraseOutput = "";
    char onFiltered[] = phraseInput.toCharArray();
    String currentFilter = new String(onFiltered);

//        for (a = 97; a <= 122; a++) {
//            a = a += 32;  
//            //char filtered[] = //second array to be printed
//        }
    char[] filtered = new char[26];
    for(int i=97;i<=122;i++){
        char a = currentFilter.charAt(i);
        filtered[i-97]= (char) (a+32);
    }
    System.out.println("filtered: " + filtered.toString());
    return phraseInput;
}
}