java中如何实现文件的读入与读出

一、文档读取

1、将文件读取为String

public static String TxtToString(File file) {
    String result = "";
    try {
        BufferedReader br = new BufferedReader(new FileReader(file));
        //构造一个BufferedReader类来读取文件
        String s = null;
        while ((s = br.readLine()) != null) {//使用readLine方法，一次读一行
            result = result + "\n" + s;
        }
        br.close();
    } catch (Exception e) {
        e.printStackTrace();
    }
    return result;
}

2、将文件读取为List集合（按行）（免费视频教程分享：java免费视频教程）

public static List<String> TxtToStringList(File file) {
    List<String> result = new ArrayList<>();
    try {
        if (!file.exists()){
            return null;
        }
        BufferedReader br = new BufferedReader(new FileReader(file));
        //构造一个BufferedReader类来读取文件
        String s = null;
        while ((s = br.readLine()) != null) {//使用readLine方法，一次读一行
            result.add(s);
        }
        br.close();
    } catch (Exception e) {
        e.printStackTrace();
    }
    return result;
}

二、Java存储文件

1、将list按行写入到txt文件中

public static void writeFileContext(List<String> strings) throws Exception {
    File file = new File("D:\IntellijIDEAProject\KeChenSheJi\data\WordLibrary_index");
    //如果没有文件就创建
    if (!file.isFile()) {
        file.createNewFile();
    }
    BufferedWriter writer = new BufferedWriter(new FileWriter
    ("D:\IntellijIDEAProject\KeChenSheJi\data\WordLibrary_index"));
    for (String l:strings){
        writer.write(l + "\r\n");
    }
    writer.close();
}

2、按照名字将string类型的集合存入文件

public static void writeFileContext_Find(List<String> strings,String name) throws Exception {
    File file = new File("D:\IntellijIDEAProject\KeChenSheJi\data\wordIndex");
    //如果没有文件就创建
    if (!file.isFile()) {
        file.createNewFile();
    }
    BufferedWriter writer = new BufferedWriter(new FileWriter
    ("D:\IntellijIDEAProject\KeChenSheJi\data\wordIndex\"+name));
    for (String l:strings){
        writer.write(l + "\r\n");
    }
    writer.close();

3、将Sting类型的list集合按文件地址存储

public static void writeFileContext_Found(List<String> strings,String filename) throws Exception {
    File file = new File(filename);
    //如果没有文件就创建
    if (!file.isFile()) {
        file.createNewFile();
    }
    BufferedWriter writer = new BufferedWriter(new FileWriter
    ("D:\IntellijIDEAProject\KeChenSheJi\data\file_index\"+file.getName()));
    for (String l:strings){
        writer.write(l + "\r\n");
    }
    writer.close();
}

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