1：(递归)有一个字符串，根据输入参数m，找出字符串的m个字符的所有字符串
例如
String str ="abc", m=2 得到结果是 "ab" "ac" "bc"
String str ="abcd" , m=3 得到结果是"abc" "acd" "bcd" "abd"
public class CalCountSuan {
public static List<String> choose(String target, int m) {
List<String> resultList = new LinkedList<>();
doChoose(resultList, target, "", m, 0);
return resultList;
}
private static void doChoose(List<String> resultList, String target, String resultStr, int m, int head) {
// 递归头
if (resultStr.length() == m) {
resultList.add(resultStr);
return;
}
// 递归体
for (int i = head; i < target.length(); i++) {
doChoose(resultList, target, resultStr + target.charAt(i), m, i+1);
}
}
public static void main(String[] args) {
List<String> list = choose("abcdefssss",3);
HashSet<String> hashSet = new HashSet<>(list);
System.out.println(hashSet+"/n"+hashSet.size());
}
}
2：计算每个城市个数
/**
* 通过Map计算重复值次数
*/
public class CalCount {
private static final Map<Object,Object> map = new HashMap<Object,Object>();
public static void main(String[] args) {
String s = "长沙,湘潭,湘西,长沙,娄底,株洲,娄底,";
String [] array = s.split(",");
if(array.length>0){
for(int i = 0; i < array.length; i++) {
if(map.containsKey(array[i])) {
Integer count = (Integer) map.get(array[i]);
count++;
map.put(array[i], count);
} else {
map.put(array[i], 1);
}
}
System.out.println(map);
}
}
}
3：
package com.bailiangroup.osp.modules.mp.test;
import java.util.Date;
import org.joda.time.DateTime;
import com.alibaba.fastjson.JSON;
import com.fasterxml.jackson.databind.ObjectMapper;
public class TimeDateObjectMapper {
private static final ObjectMapper MAPPER = new ObjectMapper();
public static void main(String [] args){
DateTime time = new DateTime();
DateTime days = time.minusDays(1).minusMinutes(44);//向前推
DateTime hours = time.plusHours(2);//向后退
Date date = hours.toDate();
System.out.println(date);
try {
net.sf.json.JSONObject object = new net.sf.json.JSONObject();
//这个是去除为空的字段过滤掉 阿里巴巴
MpUsers mpUsers = new MpUsers();
String string = net.sf.json.JSONObject.fromObject(mpUsers).toString();
System.out.println(string);
String jsonString = JSON.toJSONString(mpUsers);
System.out.println(jsonString);
// Object object = MAPPER.readValue("json",MAPPER.getTypeFactory().constructCollectionType(List.class, Object.class));
// Object readValue = MAPPER.readValue("json",Object.class);
} catch (Exception e) {
e.printStackTrace();
}
}
}
转义
public static void main(String[] args) {
String input="<pre class="brush: java;">";
String script = StringEscapeUtils.unescapeHtml3(input);
String input1=StringEscapeUtils.escapeHtml3(script);
System.out.println(script);
System.err.println(input);
int int1 = RandomUtils.nextInt(1000, 9999);
System.out.println(int1);
}
