java_temp

● 读取类所在的绝对路径

Class c = this.getClass();
String classPath = "/" + c.getName().replace('.', '/') + ".class";
String path = c.getResource(classPath).getPath();
int end = path.lastIndexOf('!'); //是否被打成jar
if (end == -1){
    System.out.println(c.getResource("/").getPath());
}
else{
    while(end > 0 && path.charAt(end) != '/') end --;
    int start = path.indexOf('/');
    System.out.print(path.substring(start, end + 1));
}

● 中文与unicode互转

public String toUnicode(String chiness){
	if (chiness == null) return null;
	StringBuilder sb = new StringBuilder();
	for (int i = 0; i < chiness.length(); i ++){
		sb.append("\\u").append(Integer.toHexString(chiness.charAt(i) & 0xffff));
	}
	return sb.toString();
}
public String toChiness(String unicode){
	if (unicode == null) return null;
	StringBuilder sb = new StringBuilder();
	String[] chars = unicode.split("\\\\u");
	for (int i = 1; i < chars.length; i ++){
		sb.append((char)Integer.parseInt(chars[i], 16));
	}
	return sb.toString();
}

● MD5加密

public static String md5(String src){
	if (src == null)
		return null;
	try{
		MessageDigest md = MessageDigest.getInstance("MD5");
		md.update(src.getBytes());
		StringBuilder dist = new StringBuilder();
		for (byte b : md.digest()){
			String s = Integer.toHexString(0xFF & b);
			if (s.length() == 1) dist.append("0");
			dist.append(s);
		}
		return dist.toString();
	}
	catch (Exception e){
		throw new RuntimeException(e);
	}
}

● native2ascii的使用
native2ascii [options] [inputfile [outputfile]]
说明：
-reverse
   Perform the reverse operation: convert a file with Latin-1 and/or
Unicode encoded characters to one with native-encoded characters.

-encoding encoding_name
    Specify the encoding name which is used by the conversion procedure.
The default encoding is taken from System property file.encoding. The
encoding_name string must be taken from the first column of the table of
supported encodings in the Supported Encodings document.

-Joption
    Pass option to the Java virtual machine, where option is one of the
options described on the reference page for the java application launcher.

For example, -J-Xms48m sets the startup memory to 48 megabytes

举例：native2ascii -reverse -encoding utf8 DevDescrib.java DevDescrib_.java

● 获取本机IP地址
InetAddress[] ips = InetAddress.getAllByName(InetAddress.getLocalHost().getHostName());
for (InetAddress ia : ips){
System.out.println(ia.getHostAddress());
}

● 正则表达式的贪婪模式与非贪婪模式
    用*匹配任意多的字符时，默认为贪婪模式，即匹配尽量多的字符。如用a.*b来匹配a11ba22b，将会匹配整个字符串。
    如果使用非贪婪模式，只需在*后面添加?，即匹配尽量少的字符。还是上面的例子，改用a.*?b来匹配，则匹配两个字符串：a11b和a22b。

● 发送POST请求，注意参数的格式

URL url = new URL("http://jscompress.com/");
HttpURLConnection connection = (HttpURLConnection)url.openConnection();
connection.setRequestMethod("POST");
connection.setDoOutput(true);
OutputStreamWriter out = new OutputStreamWriter(connection.getOutputStream(), "utf-8"); 
 //发送请求参数，注意，参数一定要用URLEncoder.encode()，否则遇到一些字符不正常，如'+'
out.write("param_name=" + URLEncoder.encode("param_value", "utf-8"));
out.flush();
out.close();