如何使用.properties文件中的条目创建哈希映射

Question

I want to create a Hash Map with the entries from .properties file. My property file looks like:

##AA
key1 = A1
key2 = A2
key3 = A3
##BB
key1 = B1
key2 = B2
key3 = B3
##CC
key1 = C1
key2 = C2
key3 = C3, C4
##DD
key1 = D1
key2 = D2
key3 = D3, D4

I will be maintaining AA, BB, CC, DD in an excel sheet.

row1 = AA
row2 = BB
row3 = CC
row4 = DD

I want to iterate through all the rows and when it is in 1st row, it should enter

key1 = A1
key2 = A2
key3 = A3

into an hashmap

2nd row it should enter

key1 = B1
key2 = B2
key3 = B3

into an hashmap and so on....

It should add the keys and values into the same hash map for every iteration and should clear the previous entries from the hash map

Answer 1

You can try something like below:-

Properties MyPropertyFile= new Properties();
FileInputStream ip = new FileInputStream(".properties file path");
MyPropertyFile.load(ip);

String row="AA"; //write logic to get row value from excel sheet and update in a variable.

HashMap<String, String> map=new HashMap<String, String>();
Set<Object> keys = MyPropertyFile.keySet();

for(Object k:keys){
    String key=(String) k;
    String value=MyPropertyFile.getProperty(key);

    if(row.charAt(0)==value.charAt(0))// check row's first character and values first character are same.
        map.put(key, value);
    }
}

Answer 2

Properties files are commonly read using java.util.Properties . However, since you have the same keys defined multiple times, only one of the values for each key will be available after processing the file. This means you will need to read the file manually (perhaps BufferedReader ), parse each line, and build the map you want.

Clearing the hashmap between iterations doesn't make much sense though unless you are making a new map each iteration or doing something with the result. Again, a HashMap can only store a single value per key, so you will need another data structure to hold what it seems like you might need.

Answer 3

As far as I understand your question, you want to pick a set of key-value pairs from the properties file, based on the comments (##AA, ##BB etc) that you have in the properties file.

Remember, in general, the 'key' should not be repeated in a property file. If it is repeated, then it will always fetch the last value. For example, if you try to retrieve value for 'key1', it will return you 'D1' always. You could try naming your keys as key1AA, key2AA, key3AA, key1BB, key2BB and so on.

Also, if you try to retrieve 'key3', you will get the complete value 'D3, D4'.

Here is an example I tried with your properties file:

package com;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;
import java.util.PropertyResourceBundle;
import java.util.ResourceBundle;

public class PropertiesToMap {

    public static void main(String[] args) {
        FileInputStream fis;
        try {
            fis = new FileInputStream("D://MyProps.properties");
            ResourceBundle resources = new PropertyResourceBundle(fis);
            Map<String,String> map = new HashMap<String,String>();

            //convert ResourceBundle to Map
            Enumeration<String> keys = resources.getKeys();
            while (keys.hasMoreElements()) {
                String key = keys.nextElement();
                map.put(key, resources.getString(key));            
            }
            //Now you can use the 'map' object as you wish.

        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }


    }

}