public class AssetAllocationBean { 
    public MAP<ID,Asset__c> assetMap { 
                                        get {
                                            if(assetMap == null) {
                                                assetMap = new Map<ID,Asset__c>();                                              
                                            }
                                            return assetMap;
                                        }
                                        set;
                                    }                                                                                    
    public Map<String,List<Investment_Asset__c>> investmentAssetMap { get;set;}
    public Map<ID,Insurance__c> insuranceMap { get;set;}    

    // ID will be Goal ID
    public Map<ID,List<GoalAssetAssociation__c>> goalAssetAssociationMap {get;set;}
    public Map<ID,List<GoalInvestmentAssetAssociation__c>> goalInvAssetAssociationMap {get;set;}
    public Map<ID,List<GoalInsuranceAssociation__c>> goalInsuranceAssociationMap {get;set;}
    
    
    public List<AssetRecordTypeBean> assetRecordTypeBeanList { 
                                                            get {
                                                                    if(assetRecordTypeBeanList == null) {
                                                                        assetRecordTypeBeanList = new List<AssetRecordTypeBean>();
                                                                    }
                                                                    return assetRecordTypeBeanList;
                                                                }   
                                                            set;
                                                        }

        
        public List<GoalAssetMapping>  goalAssetMappingList {get {
                                                                    if(goalAssetMappingList == null) {
                                                                        goalAssetMappingList = new List<GoalAssetMapping>();
                                                                    }
                                                                    return goalAssetMappingList;
                                                                } 
                                                                set;}
        
        public GoalAssetMapping populateGoalAssetMappingList(ID goalId,String assetAllocated) {
            GoalAssetMapping bean = new GoalAssetMapping();
            bean.index = goalAssetMappingList.size();
            bean.goalId = goalId;
            bean.assetAllocated = assetAllocated;
            goalAssetMappingList.add(bean);
            return bean;
        }
    public void populateGoalAssetMappingList(GoalAssetMapping mappingBean) {            
            mappingBean.index = goalAssetMappingList.size();
            goalAssetMappingList.add(mappingBean);            
    }   
    }   
    
    public class GoalAssetMapping {
        public Integer index {get;set;}
        public ID goalId {get;set;} 
        public String goalAssetAssociationId;                    
        public Decimal goldAllocatedPercent { get;set;}
        public Decimal debtAllocatedPercent {get;set;}
        public Decimal equityAllocatedPercent {get;set;}                    
        public String assetAllocated {
                                        get {
                                            if(assetAllocated == null){
                                                assetAllocated = '';                                                
                                            }
                                            return assetAllocated;
                                        }
                                        set;
                                    }
    }
    
}

Where are you creating your AssetAllocationBean records and setting up the assetmap?  I can't see anything in that code that is populating the map.

I am also not getting why it is not accessing,

Since it is not getting values so can u please tell me from where it is trying to fetch values or general idea that whenever I create get & set method then from where it fetches values so that i can try to solve it..

Is their any idea to fill values in it so that porblem will get solved..

Presumably you have some code in your system that is creating an AssetAllocationBean?

As there isn't any code in the bean itself to populate the assetMap, should you be setting up the assetMap when you create it?  If not, how are you planning to set the values?

Can u just give me an idea or little bit code to initialize my bean. 

As i am doing that I have created getAssetMap method in controller which put the key & values in it...

Following is the code...

But tell me also that it is returning value as assetMap & redmarked text will not assign the value...

    /*
      Asset Map is holding ALL assets for any given parent and its child entities
    */
    private Map<ID,Asset__c> getAssetMap(String entityId) {
        Map<ID,Asset__c> assetMap = new Map<ID,Asset__c>();
      
      try {        
          List<Asset__c> assetList;
          assetList = databaseObj.getAssets(entityId);
        
          for(Asset__c asset : assetList) {
              assetMap.put(asset.Id,asset);
      }
      }catch(Exception ex) {
         throw new GeneralException('AssetAllocationService.getAssetMap : Internal Error ' + ex.getMessage());  
        }       
        return assetMap;    
    }