Basic Java Usage

usage.java

/* MARK 使用Matcher.quoteRepalcement()过滤特殊字符 */
matchRes.appendReplacement(sb, Matcher.quoteReplacement(replacement));

// 格式化日期
new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(System.currentTimeMillis());

public void getNdayBefor(int n){
      SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
		Calendar now = Calendar.getInstance();
		now.set(Calendar.DATE, now.get(Calendar.DATE) - n);
		System.out.println(sdf.format(now.getTime()));
    return now.getTime();
}

// 筛选目录中的.java件
// 使用了匿名内部类，FilenameFilter是个借口
new File(".").list(new FilenameFilter(){
    public boolean accept(File dir, String name){
      return name.endswith(".java");
    }
  });
  
// Java IO
// Buffered input file
BufferedReader in = new BufferedReader(new FileReader("file.name"));
while(in.readline()!=null){}

// Input from memory
StringReader sin = new StringReader("source string");

// Formatted memory input
DataInputStream din = new DataInputStream(new ByteArrayInputStream("source string for bytes".getBytes()));

// Basic file ouput
PrintWriter pout = new PrintWriter(new BufferedWriter(new FileWriter("file.name")));

// Storing and Recovering Data DataOutputStream vs DataInputStream
// Alternatively using RandomAccessFile
RandomAccessFile rf = new RandomAccessFile("file.name", "rw");

// Reading binary files
BufferedInputStream bf = new BuferedInputStream(new FileInputStream("file.name"));
try{
    byte[] data = new byte[bf.available()];
    bf.read(data);
} finnaly {
    bf.close();
}

// Process Control
Process proc = new ProcessBuilder("javap HelloWorld".split()).start();// Runtime.getRuntime().exec("javap HelloWorld")
BufferedReader results = new BufferedReader(new InputStreamReader(process.getInputStream()));//得到子程序标准输出流
BufferedReader errs = new BufferedReader(new InputStreamReader(process.getErrorStream()));//得到子程序标准输出流