[SalesForce] Use CONTAINS in Visualforce Page Map

This controller:

public class MyController {
    public Map<String, List<String>> myMap {
        get {
            return new Map<String, List<String>>{
                    'abc' => new List<String>{'123', '456'},
                    'def' => new List<String>{'654', '321'}
                    };
        }
    }
}

and page:

<apex:page controller="MyController">
    <apex:repeat value="{!myMap}" var="key">
        <apex:pageBlock >
            <apex:pageBlockTable value="{!myMap[key]}" var="listItem">
                <apex:column value="{!listItem}"/>
            </apex:pageBlockTable>
        </apex:pageBlock>
    </apex:repeat>
</apex:page>

produces the expected repeated page block tables (as the apex:repeat automatically iterates over the map keys).

So I think your problem lies in the code that builds myMap or in the code that exposes it from your controller and you have not posted that code.

Java has multiple map classes such as LinkedHashMap that preserve insertion order but Apex only has one map type which does not. So in Apex a work-around is to keep a separate list of the keys as lists preserve insertion order and get the keys to iterate through from the list:

private Map<string, groupingWrapClass> map_lineitems_Group
        = new Map<string, groupingWrapClass>();
private List<String> ordered_keys = new List<String>();

private void addToMap(String key, groupingWrapClass grouping) {
    map_lineitems_Group.put(key, grouping);
    ordered_keys.add(key);
}

private void xyz() {
    ...
    addToMap('XYZ', keyvalues);
    addToMap('ABC', keyvalues);
    ...
    // Run through the map keys in insertion order
    for (String key : ordered_keys) {
        groupingWrapClass grouping = map_lineitems_Group.get(key);
        ...
    }
}

PS

On exposing this to Visualforce, make both ordered_keys and map_lineitems_Group visible (add getters or make properties) and then e.g.:

<apex:pageBlockTable value="{!ordered_keys}" var="ordered_key">
<apex:column headerValue="Year Name" value="{!map_lineitems_Group[ordered_key].yearname}"/>
...
</apex:pageBlockTable>

as expressions in Visualforce use [] for map access.

You could also add an apex:variable to factor out the common map_lineitems_Group[ordered_key] expression.