如何在arraylist中搜索元素？

Question

Example is I want to search code A25 and A29 then it will print it? I cant seems find the syntax for searching long words in arraylist.

    ArrayList<String> arrList = new ArrayList<String>();
    arrList.add("A25            CS 212          Data Structures         3");
    arrList.add("A26            IT 312          Data Base Management System 2   3");
    arrList.add("A27            IT 312          Data Base Management System 2   3");
    arrList.add("A28            IT 212          Data Base Management System 2   3");
    arrList.add("A29            CS 313          Digital Design          3");
    arrList.add("A30            IT 212          Discrete Structures     3");
    arrList.add("A25            IT 212          Discrete Structures     3");
    arrList.add("984            Engl 3          Speech and oral Communication   3");
    arrList.add("582            Theo 3          Christ and Sacraments       3");
    arrList.add("470            Stata1          Probablility and Statistics 3");
    arrList.add("999            Dota 2          Dota Guide          3");
    System.out.println("Enter code to search");
    int code = scan.next();
    //Desired output
   Enter code to search: 
   A29
   A30

   A29          CS 313          Digital Design          3
   A30          IT 212          Discrete Structures     3
   //

Answer 1

您最好创建一个类并将该属性（如branch，rollno..etc）添加到该类，并将该类的对象添加到arrayList并进行迭代和比较以查找您正在查找的特定属性。现在很难搜索如此大的字符串和虽然看起来很糟糕。

Answer 2

How about this?

String code = scan.nextLine();
for (String s : arrList) {
  if (s.startsWith(code)) {
    System.out.println(s);
    break; //optional, depending on your use case
  }
}

It should output exactly what you want.

Answer 3

Try the below code

ArrayList<String> arrList = new ArrayList<String>();
        arrList.add("A25            CS 212          Data Structures         3");
        arrList.add("A26            IT 312          Data Base Management System 2   3");
        arrList.add("A27            IT 312          Data Base Management System 2   3");
        arrList.add("A28            IT 212          Data Base Management System 2   3");
        arrList.add("A29            CS 313          Digital Design          3");
        arrList.add("A30            IT 212          Discrete Structures     3");
        arrList.add("A25            IT 212          Discrete Structures     3");
        arrList.add("984            Engl 3          Speech and oral Communication   3");
        arrList.add("582            Theo 3          Christ and Sacraments       3");
        arrList.add("470            Stata1          Probablility and Statistics 3");
        arrList.add("999            Dota 2          Dota Guide          3"); 
     List <String> searchResult = new ArrayList<String>(); 
               for (String content : arrlist) {
                   if(content.matches("a29")){
                       searchresult.add(content);
                   }
               }

Answer 4

try this

List <String> codes = new ArrayList<String>();//list of codes to search
codes.add("A25");
codes.add("A29");
List <String> result = new ArrayList<String>();//list of search results
for(String s:arrList)
    for(String code:codes)
        if (s.startsWith(code))
            result.add(s);
for(String s:result)
     System.out.println(s)

Answer 5

Instead of iterating through all the array list for every input search code, you can create one hashmap to store key, value pair as follows :

HashMap<String,String> map = new HashMap<String,String>();
map.put("A25","CS 212          Data Structures         3");
map.put("A26","IT 312          Data Base Management System 2   3");
.....
.......

Now, it is really easy to get the element by code . Use HashMap#get(key) method

String code = scan.nextLine();
System.out.println(code + " " + map.get(code));

This is your desired output.

But, I would say @Task's answer is the correct one.