Question

好的，我试图每三个字母添加一个新行。目标是拥有20行随机大写字母。每行3个大写字母。

我将数字随机化，然后将它们转换为字符串。然后输出字符串。我在一个直的字符串中有60个随机大写字母，但我无法弄清楚如何添加新行，因为每个字母都是随机的，我不能像以前那样告诉java搜索什么。我已经尝试使用if语句并在最后添加一个“/ n”，但它只是变得混乱和困难。操作员命令我无法弄清楚如何应用每三个字母。

以下是我目前在“wrightRandomCodesToFile”下的代码

package mp05;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.PrintWriter;
import java.util.Random;
import java.util.Scanner;

public class Main {
    private static final int PRODUCT_COUNT = 20;
    private static final int CHARACTERS_PER_CODE = 3;
    private static int charA;
    private static int preChars;
    private static String preLetters;

    public static void main(String[] args) {
        /* (1) Generate three character alphabetic prefix codes. */
        writeRandomCodesToFile("prefix.txt", 'A', 'Z',
                              CHARACTERS_PER_CODE, PRODUCT_COUNT);
        // when you hit run, there is 3 numbers. six digits though.

        /* (2) Generate three character alphabetic suffix codes. */
        writeRandomCodesToFile("suffix.txt", 'A', 'Z',
                               CHARACTERS_PER_CODE, PRODUCT_COUNT);

        /* (3) Generate three character numeric inline codes. */
        writeRandomCodesToFile("inline.txt", '0', '9',
                               CHARACTERS_PER_CODE,  PRODUCT_COUNT);

        /* (4) Merge the two alphabetic and one numeric code to produce the
         * final product code. */
        mergeProductCodesToFile("prefix.txt", "inline.txt", "suffix.txt",
                                "productCode.txt");
    }// end main()


    /* (1),(2),(3) Generate the alphanumeric codes. These are three aphanumeric
     * character combinations generated randomly with each character in the
     * range A-Z | 0-9. Thus you will have codes from AAA-ZZZ | 000-999.
     *
     * Write numberOfCodesToGenerate codes to the specified file.
     */
    public static void writeRandomCodesToFile(String codeFile,
                                              char fromChar, char toChar,
                                              int numberOfCharactersPerCode,
                                              int numberOfCodesToGenerate) {
        Random rnd = new Random();
        charA = 65;
        for (int i = 1; i <= 20; i++) {
            try (
                PrintWriter fout = new PrintWriter(new File("prefix.txt")); //Creates File
            ) {
                preChars = charA + rnd.nextInt(26);
                preLetters = String.valueOf((char) preChars);
                System.out.print(preLetters);    

            } catch (FileNotFoundException e) {
                 System.err.println(e.getMessage());
            }
        }
    }// end writeRandomCodesToFile()

    /* (4) Merge the two alphabetic and one numeric code to produce the final
     * product code. The final product code will consist of <prefix><inline><suffix>.
     * Each code will be in the range AAA000AAA-ZZZ999ZZZ.
     *
     * Merge by using a prefix, an inline and a suffix code from their corresponding
     * files. Each individual code (pre, in, post) is used exactly once, and all values are used.
     *
     * Write these final product codes to the file specified in productFile.
     */
    public static void mergeProductCodesToFile(String prefixFile,
                                               String inlineFile,
                                               String suffixFile,
                                               String productFile) {


    }// end mergeProductCodesToFile()
}// end Main

Answer 1

忽略您的背景并按照标题回答问题：

给定一个长字符串，每3个字符插入一个换行符：

str = str.replaceAll("...", "$0\n");

Answer 2

import java.util.Random;
import java.io.PrintWriter;
class test{

    public static String randomString(String chars, int length) {
        Random rand = new Random();
        StringBuilder buf = new StringBuilder();
        for (int i=0; i<length; i++) {
            buf.append(chars.charAt(rand.nextInt(chars.length())));
        }
        return buf.toString().replaceAll("...","$0\n");
    }

    public static void main(String[] args ) {
        String myString = randomString("ABCDEFGHIJKLMONQRSTUVWXYZ",60);

        try {
            PrintWriter pw = new PrintWriter("fileame.txt");
            pw.println(myString);
            pw.close();
        } catch (Exception e) {}
    }
}

每三个数字添加一个新行

2 个答案: