Storing variables to a map by splitting a text file
Range-based for loop


for (int i = 0; i &lt; textList.size(); i++){
    String[] split = splitTxt(textList.get(i), "\\s+");



You can simplify this with a range-based for loop.  

for (String text : textList) {
    String[] split = text.split("\\s+");


No need to manage i manually.  

I also eliminated the call to splitTxt, which makes the code smaller and easier to read.  

Bug


    List&lt;String&gt; friends = new ArrayList&lt;&gt;();
    List&lt;String&gt; interests = new ArrayList&lt;&gt;();
    if (split.length &gt;= 2){
        String[] interestArray = splitTxt(split[2], ";");



This will cause an array index out of bounds when the split.length is 2.  

    if (split.length &lt; 3) {
        continue;
    }

    String[] interestArray = splitTxt(split[2], ";");
    List&lt;String&gt; friends = new ArrayList&lt;&gt;();
    List&lt;String&gt; interests = new ArrayList&lt;&gt;();


When split is of length 2, only 0 and 1 are valid indexes.  So split[2] would be out of bounds.  Making it a 3 instead of a 2 would fix that.  

Switching to an early exit changes from &gt;= to &lt; and allows us to reduce the level of indent.  It works here because the entire code for an iteration after that point is inside the if.  

There is no point to declaring and initializing friends and interests if we're not going to use them.  So do those tasks after the check, not prior.  

asList


        String[] interestArray = splitTxt(split[2], ";");
        for(int j = 0; j &lt; interestArray.length; j++){
            interests.add(interestArray[j]);
        }
        Accounts.put(split[0],split[1]);
        intrestDic.put(split[0],interests);



You don't need to manually copy one by one.  

        Accounts.put(split[0],split[1]);
        intrestDic.put(split[0], new ArrayList&lt;String&gt;(Arrays.asList(split[2].split(";"))));


Using a copy constructor with Arrays.asList will allow the whole thing to be copied at once.  

Summary

private static final int HEADER_SIZE = 3;


and later 

for (String text : ReadFile(FileName)) {
    String[] split = text.split("\\s+");
    if (split.length &lt; HEADER_SIZE) {
        continue;
    }

    Accounts.put(split[0], split[1]);
    intrestDic.put(split[0], new ArrayList&lt;String&gt;(Arrays.asList(split[2].split(";"))));
    List&lt;String&gt; friends = Arrays.asList(split).subList(HEADER_SIZE, split.length));
    FriendsDic.put(split[0], new ArrayList&lt;String&gt;(friends);
}


This isn't necessarily more efficient, although it could be (depending on how Java optimizes it).  The primary advantage of this version is that it leaves maintenance to the Java engine.  

Hibernate

Hibernate (and Java Persistence Annotations in general) is for exactly this task.  It maps classes to storage and vice versa.  Now, that might be a heavyweight solution, but it is one that exactly addresses the problem.  

You can write persistence code manually, without annotations.  But I would generally still use a database if you intend the code to scale at all.  You don't want to read all the records every time you want one record.  Rather than reinventing that wheel, just use the existing solution:  a database.  

Hibernate makes it comparatively easy to switch from one database to another.