ListFrame<Map> lines = ListFrame.fromList(list);
double sum = lines.get("value").sum();
lines = lines
        .handle("value=format(value,2)") //round to the nearest hundredth
        .handle(line->line.getName()==null,"name=''") //if(line.getName()==null){line.setName('');}
        .handle(line->line.getValue()==null,"value=0","value=value+2") //value = line.getValue()==null?0:line.getValue()+2;
        .handle("name=replace(name,'#','')") //replace '#' to ''
        .handle("percent=double(value)/"+sum) //converting value's tyle to double and computing percent
        .groupBy("name").sum("percent"); //groupBy 'name'

ListFrame<Metric> lines = ListFrame.fromList(list);
double sum = lines.get("value").sum();
lines = lines
        .addHandler("value=format(value,2)") 
        .addHandler("name=replace(name,'#','')")
        .addHandler("percent=double(value)/"+sum) 
        .execute()
        .groupBy("name").sum("percent"); //groupBy 'name'

ListFrame<Metric> lines = ListFrame.fromList(list);
lines = lines
        .addHandler(new DataHandler1()) 
        .addHandler(new DataHandler2()) 
        .addHandler(new DataHandler3()) 
        .addHandler(new DataHandler4()) 
        .execute();
//DataHandler1、2、3、4需要实现DataHandler接口

Datasource datesource = xxx;
ListFrame list = new ListFrame();
list.initDataSource(datesource);

ListFrame<Map<String,Object>> lines = list.readSql("select * from xxx").handle(a->...).handle(a->...)...;

ListFrame<String> lines = ListFrame.readString("test.txt");
lines = lines
    .handle(line -> line + ";") //add ";" at the end of every line
    .handle(line -> "=>"+line ); //add "=>" at the front of every line

/*read easily*/
//ListFrame<Map<String, Object>> lines = ListFrame.readMap(path);
/*read by split symbol*/
//ListFrame<Map<String, Object>> lines = ListFrame.readMap(path,",");
/*define data types*/
ListFrame<Map<String, Object>> lines = ListFrame.readMap(path,new Class[]{Integer.class,String.class,Integer.class,Double.class});
lines = lines
        .handle("收入=收入*0.8")
        .handle("序号='0'+序号;姓名=序号+姓名")//add "0" at the front of 序号;rename 姓名 by 序号+姓名
        .handle(new MapHandler());//add a key named "newKey" whose value is 1  ;MapHandler can be seen as follows

public class MapHandler implements DataHandler<Map<String, Object>> {
    @Override
    public Map<String, Object> handle(Map<String, Object> line) {
        line.put("newKey",1);
        return line;
    }
}

lines = lines(map->{
  map.put("newKey",1);
  return map;
});

/*obtain data by column name*/
ListFrame<Double> indexs = lines.get("收入");
/*you can user ObjectName::getXX if ListFrame's elements are java objects*/
//ListFrame<Integer> indexs = lines.get(User::getAge);
double maxIncome = indexs.max();
double minIncome = indexs.min();
double avgIncome = indexs.avg();
/*the index of max*/
int argmax= listFrame.argmax();
/*the index of min*/
int argmin= listFrame.argmin();

MapFrame<Object, ListFrame> agesGroup = lines.groupBy("年龄");
MapFrame<Object, Integer> count = agesGroup.count();
MapFrame<Object, Double> incomeAvg = agesGroup.avg("收入");
MapFrame<Object, Double> incomeSum = agesGroup.sum("收入");
MapFrame<Object, ListFrame> incomeConcat = agesGroup.concat("收入");
/*continuous groupBy*/
MapFrame<Object, MapFrame<Object, ListFrame>> incomeAgeConcat = lines.groupBy("收入").groupBy("年龄");

/*save to file*/
lines.toFile("save.txt");

List<Object> list = ...;
ListFrame<Object> lines = ListFrame.fromList(list);
list = lines.toList();

ListFrame<Map> lines = ListFrame.readMap(path);
ListFrame<User> users = lines.toObjectList(User.class);
ListFrame<Map> maps = users.toMapList();

/*replace "xxx" to "yyy"*/
lines = lines.replace("需要替换的列","xxx","yyy");

List<String> list = Arrays.asList("1","2","3","4");
ListFrame<Integer> listFrame = ListFrame.fromList(list );
ListFrame<Integer> listInt= listFrame.asInteger();
ListFrame<Double> listDouble= listFrame.asDouble();
ListFrame<Float> listFloat= listFrame.asFloat();
ListFrame<String> listString= listFloat.asString();

List<Integer> list = Arrays.asList(2,2,2,4);
MapFrame<Integer,Integer> listFrame = ListFrame.fromList(list).frequency()
/*得到map {2=3,4=1}*/

List<Integer> list = Arrays.asList(2,2,2,4);
ListFrame<Integer> listFrame = ListFrame.fromList(list );
listFrame.variance();//方差
listFrame.standardDeviation();//标准差

List<Integer> list = Arrays.asList(2,null,2,null,6);
ListFrame<Integer> listFrame = ListFrame.fromList(list );
listFrame = listFrame.dropNull();

//[2,null,2,null,6]->[2,2,6]

List<Integer> list = Arrays.asList(2,2,2,6,6);
ListFrame<Integer> listFrame = ListFrame.fromList(list );
listFrame = listFrame.distinct();

//[2,2,2,6,6]->[2,6]

ListFrame<Map<String, Object>> lines = xxx;
/*convert code to int*/
lines = lines.handle("id=int(code)");

/*convert value to double*/
lines = lines.handle("percent=double(value)");

/*convert value to string*/
lines = lines.handle("name=string(value)");

/*substring is like java substring*/
lines = lines.handle("name=substring(name,1,2)");

/*replace "xxx" to "yyy"*/
lines = lines.handle("name=replace(name,'xxx','yyy')");
/*you can alse use '-' to replace if you only want to replace 'xxx' */
lines = lines.handle("name=name-'xxx'");

/*index is like java indexof*/
lines = lines.handle("id=index(name,'xxx')");

/*round to the nearest hundredth*/
lines = lines.handle("percent=format(percent,2)");