目前包含的内容有:
- 将变量转换成静态常量值或枚举值
- 将数据库字段解析为变量
- Java使用FileChannel实现大文件读取、写入、复制、倒序复制
- 正则表达式匹配
- 根据年月日生成文件
输入：
helloWorldProperty
输出：
HELLO_WORLD_PROPERTY
方法:
/**
* 变量转化成常量
* @param param
* @return
*/
private static String variable2Constant(String param){
char[] array = param.toCharArray();
String result = "";
for(int i=0;i<array.length;i++){
result += array[i];
// 防止数组越界
if(i+1==array.length){
result = result.toUpperCase();
break;
}
// 遇到下一个为大写字母前面要加一个_
if('A'<=array[i+1] && array[i+1]<='Z'){
result += "_";
result = result.toUpperCase();
}
}
return result;
}输入：
userId,用户ID
输出：
/**
* 用户ID
*/
private String userId;
方法:
/**
* 解析数据库字段
* @param inputDbColumn 输入格式为 userId,用户ID
* @return
*/
private static String parse(String inputDbColumn){
String[] array = inputDbColumn.split(",");
return parseNote(array[1]) + "\n" + parseProperty(array[0]);
}
/**
* 生成注释
* @param comment
* @return
*/
private static String parseNote(String comment){
return String.format("/**\n" +
" * %s\n" +
" */", comment);
}
/**
* 生成变量，只针对varchar --> String
* @param value
* @return
*/
private static String parseProperty(String value){
char[] array = value.toCharArray();
StringBuffer buffer = new StringBuffer();
for(int i=0;i<array.length;i++){
if(array[i]=='_'){
// 下一位转换成大写字母
array[i+1] -= 32;
continue;
}
buffer.append(array[i]);
}
String property = String.format("private String %s;", buffer.toString());
return property;
}方法:
/**
* 写文件
* @param fileName
* @throws IOException
*/
public void doWrite(String fileName) throws IOException {
outFile = new RandomAccessFile(fileName, "rw");
outChannel = outFile.getChannel();
String newData = "New String to write to file... \n";
buf.clear();
buf.put(newData.getBytes());
buf.flip();
while (buf.hasRemaining()){
outChannel.write(buf);
}
outChannel.close();
System.out.println("Write Over!\n");
}
/**
* 读文件
* @param fileName
* @throws IOException
*/
public void doRead(String fileName) throws IOException {
inFile = new RandomAccessFile(fileName, "rw");
inChannel = inFile.getChannel();
int bytesRead = inChannel.read(buf);
while (bytesRead != -1) {
System.out.println("Read " + bytesRead);
buf.flip();
while (buf.hasRemaining()){
System.out.print((char) buf.get());
}
buf.clear();
bytesRead = inChannel.read(buf);
}
inFile.close();
}
/**
* 拷贝文件
* @param sourceFile
* @param targetFile
* @throws IOException
*/
public void doCopy(String sourceFile, String targetFile) throws IOException {
inFile = new RandomAccessFile(sourceFile, "rw");
inChannel = inFile.getChannel();
RandomAccessFile bFile = new RandomAccessFile(targetFile, "rw");
FileChannel outChannel = bFile.getChannel();
inChannel.transferTo(0, inChannel.size(), outChannel);
System.out.println("Copy over");
inChannel.close();
}
/**
* 按照行读文件
* @param fileName
* @throws IOException
*/
public void doReadLine(String fileName) throws IOException {
inFile = new RandomAccessFile(fileName, "rw");
int lineNum = 0;
inFile.seek(lineNum);
String line = "";
while((line = inFile.readLine())!=null){
line = new String(line.getBytes("UTF-8"), "UTF-8");
System.out.println(line);
}
inFile.close();
}
/**
* 倒序拷贝文件
* @param sourceFile
* @param targetFile
* @throws IOException
*/
public void reverseCopy(String sourceFile, String targetFile) throws IOException {
inFile = new RandomAccessFile(sourceFile, "r");
inChannel = inFile.getChannel();
outFile = new RandomAccessFile(targetFile, "rw");
outChannel = outFile.getChannel();
// 文件长度
long len = inFile.length();
System.out.println("文件开始指针为"+0);
//指针是从0到length-1
long nextEnd = len - 1;
String line;
//seek到最后一个字符
inFile.seek(nextEnd);
int c = -1;
while (nextEnd >= 0) {
c = inFile.read();
//只有行与行之间才有\r\n，这表示读到每一行上一行的末尾的\n，而执行完read后，指针指到了这一行的开头字符
if (c == '\n')
{
line = new String(inFile.readLine().getBytes("UTF-8"), "UTF-8");
System.out.println(line);
writeLine(line, outChannel);
}
// 当文件指针退至文件开始处，输出第一行
if (nextEnd == 0) {
//不需要为下次做准备了，但是因为read()方法指针从0到了1，需重置为0
inFile.seek(0);
line = new String(inFile.readLine().getBytes("UTF-8"), "UTF-8");
System.out.println(line);
writeLine(line, outChannel);
} else {
//为下一次循环做准备
inFile.seek(nextEnd-1);
}
nextEnd--;
}
System.out.println("Reverse Copy over");
outChannel.close();
inChannel.close();
}
private void writeLine(String line, FileChannel outChannel)throws IOException{
// 写入文件
line += "\n";
buf.clear();
buf.put(line.getBytes());
buf.flip();
while (buf.hasRemaining()){
outChannel.write(buf);
}
}文件按照行倒序输出可以使用这个命名
perl -e 'print reverse <>' filenamePatternMatch 实现一个函数用来匹配包括'.'和''的正则表达式。模式中的字符'.'表示任意一个字符，而''表示它前面的字符可以出现任意次（包含0次）。
private boolean match(char[] str, int i, char[] pattern, int j) {
if (j == pattern.length) {
return str.length == i;
}
if (j < pattern.length - 1 && pattern[j + 1] == '*') {
if (str.length != i && (str[i] == pattern[j] || pattern[j] == '.')) {
return match(str, i, pattern, j + 2) || match(str, i + 1, pattern, j);
} else {
return match(str, i, pattern, j + 2);
}
}
if (str.length != i && (str[i] == pattern[j] || pattern[j] == '.')) {
return match(str, i + 1, pattern, j + 1);
}
return false;
}为什么要做这件事情，因为看这里
生成文件关键代码
/**
* 根据文件名创建文件
* @param filename
*/
public static void createFile(String filename) {
File file = new File("./" + filename.substring(0, 6), filename);
if (file.exists()) {
System.out.println("文件名:" + file.getAbsolutePath());
System.out.println("文件大小：" + file.length());
} else {
//在.class文件所在的最上层包的父路径下
file.getParentFile().mkdirs();
try {
file.createNewFile();
} catch (IOException e) {
e.printStackTrace();
}
}
}写入文本关键代码
/**
* 向指定文件写入内容
* @param checkFile
* @param stringBuffer
* @throws IOException
*/
public static void writeTextToFile(File checkFile, StringBuffer stringBuffer) throws IOException {
FileWriter writer = null;
try {
// 1、检查目标文件是否存在，不存在则创建
if (!checkFile.exists()) {
checkFile.createNewFile();// 创建目标文件
}
// 2、向目标文件中写入内容
// FileWriter(File file, boolean append)，append为true时为追加模式，false或缺省则为覆盖模式
writer = new FileWriter(checkFile, false);
writer.append(stringBuffer);
writer.flush();
System.out.println(checkFile.getName() + "写入成功！！");
} catch (IOException e) {
e.printStackTrace();
} finally {
if (null != writer) {
writer.close();
}
}
}