获取系统默认编码：

System.getProperty("file.encoding");

Charset.defaultCharset()；也是可以的

获取当前程序运行的路径，很巧妙 HOHO

File directory  = new File(".");
directory.getCanonicalPath();

thanks to http://blog.csdn.net/hxirui/article/details/514575

hashtable的遍历方法:

第一种:

for(Iterator itr = ht.keySet().iterator(); itr.hasNext();){
String key = (String) itr.next();
String value = (String) ht.get(key);
System.out.println(key+"--"+value);
}

第二种:

Enumeration e1 = ht.elements();
while (e1.hasMoreElements()) {
System.out.println(e1.nextElement());
}

第三种:

Enumeration e2 = ht.keys();
while (e2.hasMoreElements()) {
String key = (String) e2.nextElement();
System.out.println(key +"---"+ht.get(key));
}

thanks to http://blog.csdn.net/onisland/article/details/5609762

关键在于这句:{(x, y) such that c.compare(x, y) <= 0}.

Comparator<String> comparator = new Comparator<String>(){
@Override
public int compare(String o1, String o2) {
int countO1 = word_count.get(o1);
int countO2 = word_count.get(o2);
if(countO1 > countO2){
return -1;
}else if(countO1 < countO2){
return 1;
}else{
return 0;
}
}
};
Collections.sort(sortList,comparator);

json的基本操作备份

JSONObject rootObj = JSONObject.fromObject(jsonStr);
JSONObject dataObj = rootObj.getJSONObject("data");
JSONArray infoArray = dataObj.getJSONArray("info");
for (int i = 0; i < infoArray.size(); ++i) {
JSONObject tmpObj = infoArray.getJSONObject(i);
}

java按行读取文本文件

BufferedReader reader = new BufferedReader(new FileReader(_fileAdr));
String line = reader.readLine();
while(line != null){
System.out.println(line);
line = reader.readLine();
}
reader.close();