存储字符串数组而不初始化其大小

Question

Background:这个程序读取一个文本文件并用用户输入替换文件中的单词。

问题:我正试图从文本文件中读取一行文本并将单词存储到数组中。

现在数组大小是硬编码的，用于测试目的的索引数量，但我想使数组能够读取任何大小的文本文件。

这是我的代码。

public class FTR {
public static Scanner input = new Scanner(System.in);
public static Scanner input2 = new Scanner(System.in);
public static String fileName = "C:\Users\...";
public static String userInput, userInput2;
public static StringTokenizer line;
public static String array_of_words[] = new String[19]; //hard-coded
/* main */
public static void main(String[] args) {
    readFile(fileName);
    wordSearch(fileName);
    replace(fileName);
}//main
/*
 * method: readFile
 */
public static void readFile(String fileName) {
    try {
        FileReader file = new FileReader(fileName);
        BufferedReader read = new BufferedReader(file);
        String line_of_text = read.readLine();
        while (line_of_text != null) {
            System.out.println(line_of_text);
            line_of_text = read.readLine();
        }
    } catch (Exception e) {
        System.out.println("Unable to read file: " + fileName);
        System.exit(0);
    }
    System.out.println("**************************************************");
}
/*
* method: wordSearch
*/
public static void wordSearch(String fileName) {
    int amount = 0;
    System.out.println("What word do you want to find?");
    userInput = input.nextLine();
    try {
        FileReader file = new FileReader(fileName);
        BufferedReader read = new BufferedReader(file);
        String line_of_text = read.readLine();
        while (line_of_text != null) { //there is a line to read
            System.out.println(line_of_text);
            line = new StringTokenizer(line_of_text); //tokenize the line into words
            while (line.hasMoreTokens()) { //check if line has more words
                String word = line.nextToken(); //get the word 
                if (userInput.equalsIgnoreCase(word)) {
                    amount += 1; //count the word
                }
            }
            line_of_text = read.readLine(); //read the next line
        }
    } catch (Exception e) {
        System.out.println("Unable to read file: " + fileName);
        System.exit(0);
    }
    if (amount == 0) { //if userInput was not found in the file
        System.out.println("'" + userInput + "'" + " was not found.");
        System.exit(0);
    }
    System.out.println("Search for word: " + userInput);
    System.out.println("Found: " + amount);
}//wordSearch
/*
* method: replace
*/
public static void replace(String fileName) {
    int amount = 0;
    int i = 0;
    System.out.println("What word do you want to replace?");
    userInput2 = input2.nextLine();
    System.out.println("Replace all " + "'" + userInput2 + "'" + " with " + "'" + userInput + "'");
    try {
        FileReader file = new FileReader(fileName);
        BufferedReader read = new BufferedReader(file);
        String line_of_text = read.readLine();
        while (line_of_text != null) { //there is a line to read
            line = new StringTokenizer(line_of_text); //tokenize the line into words
            while (line.hasMoreTokens()) { //check if line has more words
                String word = line.nextToken(); //get the word 
                if (userInput2.equalsIgnoreCase(word)) {
                    amount += 1; //count the word
                    word = userInput;
                }
                array_of_words[i] = word; //add word to index in array   
                System.out.println("WORD: " + word + " was stored in array[" + i + "]");
                i++; //increment array index     
            }
  //THIS IS WHERE THE PRINTING HAPPENS
            System.out.println("ARRAY ELEMENTS: " + Arrays.toString(array_of_words));
            line_of_text = read.readLine(); //read the next line
        }
        BufferedWriter outputWriter = null;
        outputWriter = new BufferedWriter(new FileWriter("C:\Users\..."));
        for (i = 0; i < array_of_words.length; i++) { //go through the array
            outputWriter.write(array_of_words[i] + " "); //write word from array to file
        }
        outputWriter.flush();
        outputWriter.close();
    } catch (Exception e) {
        System.out.println("Unable to read file: " + fileName);
        System.exit(0);
    }
    if (amount == 0) { //if userInput was not found in the file
        System.out.println("'" + userInput2 + "'" + " was not found.");
        System.exit(0);
    }
}//replace
}//FTR

Answer 1

您可以使用java.util.ArrayList(它与固定大小的数组不同动态增长)通过使用以下代码替换数组来存储字符串对象(测试文件行):

public static List<String> array_of_words = new java.util.ArrayList<>();

您需要使用add(string)添加行(字符串)，get(index)检索行(字符串)

详情请参阅以下连结:http://docs.oracle.com/javase/8/docs/api/java/util/ArrayList.html

Answer 2

你可以试试ArrayList

在Java中，普通数组不能在没有初始大小的情况下初始化，也不能在运行时扩展。而数组列表具有List接口的可调整数组实现。ArrayList还附带了许多有用的内置函数，例如

大小()

isEmpty ()

包含()

克隆()

等。除此之外，你还可以使用ArrayList函数toArray()将数组列表转换为简单数组。希望这能回答你的问题。我将准备一些代码并与您分享，以进一步解释使用List接口可以实现的事情。

Answer 3

不要使用本地[]数组，而是使用任何类型的java集合

List<String> fileContent = Files.readAllLines(Paths.get(fileName));
fileContent.stream().forEach(System.out::println);
long amount = fileContent.stream()
    .flatMap(line -> Arrays.stream(line.split(" +")))
    .filter(word -> word.equalsIgnoreCase(userInput))
    .count();
List<String> words = fileContent.stream()
    .flatMap(line -> Arrays.stream(line.split(" +")))
    .filter(word -> word.length() > 0)
    .map(word -> word.equalsIgnoreCase(userInput) ? userInput2 : word)
    .collect(Collectors.toList());
Files.write(Paths.get(fileName), String.join(" ", words).getBytes());

当然你可以更传统地使用这种列表，使用循环

for(String line: fileContent) {
    ...
}

或者

for (int i = 0; i < fileContent.size(); ++i) {
    String line = fileContent.get(i);
    ...
}

i just like streams:)