Java 常用工具方法

1.去除文件中的空行：

public class QuKongHang {
    public static void main(String[] args) throws Exception {
        File f1 = new File("E:\\1.txt");// 打开文件
        FileInputStream in = new FileInputStream(f1);
        BufferedReader read = new BufferedReader(new InputStreamReader(in, "UTF-8"));
        String line = "";
        while ((line = read.readLine()) != null) {
            if (!line.equals("")) {
                System.out.println(line);
            }
        }
        read.close();
    }
}

2.将整个文件中的某个字符替换成另一个：

public class 文件字符转换 {
    public static void main(String[] args) {
        try {
            BufferedReader bufReader = new BufferedReader(new InputStreamReader(new FileInputStream(new File("E:\\1.txt"))));//数据流读取文件
            StringBuffer strBuffer = new StringBuffer();
            for (String temp = null; (temp = bufReader.readLine()) != null; temp = null) {
                if ((temp.indexOf("for") == -1) && (temp.indexOf("if") == -1)) {
                    if (temp.indexOf("《") != -1) { //判断当前行是否存在想要替换掉的字符 -1表示存在
                        temp = temp.replace("《", "<");
                    }
                    if (temp.indexOf("》") != -1) { //判断当前行是否存在想要替换掉的字符 -1表示存在
                        temp = temp.replace("》", ">");
                    }
                }
                strBuffer.append(temp);
                strBuffer.append(System.getProperty("line.separator"));//行与行之间的分割
            }
            bufReader.close();
            PrintWriter printWriter = new PrintWriter("E:\\1.txt");//替换后输出的文件位置
            printWriter.write(strBuffer.toString().toCharArray());
            printWriter.flush();
            printWriter.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

3.List去重

public class Test {
    public static void main(String args[]) {
        List<String> oldList = new ArrayList<>();
        oldList.add("a");
        oldList.add("b");
        oldList.add("c");
        oldList.add("b");
        List<String> newList = new ArrayList<>();
        for (String cd : oldList) {
            System.out.print(cd + " ");
            if (!newList.contains(cd)) {
                newList.add(cd);
            }
        }
        System.out.println();
        for (String cd : newList){
            System.out.print(cd + " ");
        }
    }
}