3-Collections.java

@isTest
public class Collections {
    static testMethod void Lists(){
        //LISTS ARE AN ORDERED COLLECTION OF DATA
        
        //How to instantiate a List with some pre-defined values
        String someword = 'thread';
        List<String> threeStrings = new List<String>{'rope', 'twine', someword};
        
        //Lists have methods that allow us to evaluate or manipulate them
        //See https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_methods_system_list.htm
        System.assertEquals(3, threeStrings.size());
        
        //List items can be referenced by their "index" number starting with zero
        System.assertEquals('rope', threeStrings[0]);
        
        //How to Instantiate an empty List
        List<String> noStrings = new List<String>();
        System.assert(noStrings.isEmpty());
                
        noStrings.add('rock');
        System.assertEquals(1, noStrings.size());
        
      //FIX ME! Using the values in the first List we made, uncomment the two lines below and get them to pass
        System.assertEquals('rope', threeStrings[0]);
        //System.assertEquals(, threeStrings[1]);
        //System.assertEquals('thread', threeStrings[]);
        
        //Lists can also contain other lists. Think of an Accounts & Contacts Report.
        List<List<String>> numberNames = new List<List<String>>();
        numberNames.add(new List<String>{'zero', 'one', 'two', 'three', 'four'});
        numberNames.add(new List<String>{'cero', 'uno', 'dos', 'tres'});
        numberNames.add(new List<String>{'ling', 'yi', 'er'});
        System.assertEquals(3, numberNames.size());
        
        //FIX ME! Using the data in numberNames uncomment the lines below and get them to pass
        //System.assertEquals(, numberNames[2].size());
        //System.assertEquals(4, numberNames[].size());
        
        //Index notation can be chained to retrieve values in lists of lists
        System.assertEquals('zero', numberNames[0][0]);
        
        //FIX ME! Build the String in the expected values - don't forget to concatenate spaces into your string!
        //System.assertEquals('uno dos tres', );
       
        //Creating a List from a SOQL query is very common
		List<Profile> profs = [SELECT Name FROM Profile];
        System.debug('All the Profiles: ' + profs);
        
        //Note that even though we did not add ID to the SELECT, it's retreived:
        System.debug('Profile 1 ID: ' + profs[0].Id);
        
        //But any other field must be added to the SELECT to be referenced:
        //System.debug('THIS WILL NOT WORK!' + profs[0].CreatedDate);
        
        //FIX ME! Make the following assertion pass by figuring out a way to count all the Profiles
        //System.assertEquals( , profs.size());
        
        //Alternate method for creating a List: datatype first, followed by []
        //This allows you to set a "dimension" that forces the List size to be validated.
        String[] oneWord = new String[1];
        oneWord[0] = 'able';
        //oneWord[1] = 'baker';//Won't Work! The List was configured for only 1 item
        
        oneWord.add('charlie');//Will Work! The .add() method automatically expands the List
        system.debug(oneWord);
        oneWord[1] = 'baker';
        System.debug(oneWord);
        System.assertEquals(2, oneWord.size());        
    }

    static testMethod void Sets(){
    //SETS ARE AN UNORDERED COLLECTION OF UNIQUE DATA
      
        Set<String> planets = new Set<String>{'Mars', 'Earth', 'Pluto'};
        System.assertEquals(3, planets.size());
        
        //Sets enforce uniqueness so you don't have to check whether a value is already in a Set
    	Set<String> months = new Set<String>();
        months.add('June');
        months.add('July');
        months.add('June');
        System.assertEquals(2, months.size());
        
        //Sets have some similar methods to Lists like add() and some useful others like contains()
        //See https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_methods_system_set.htm
        System.assert(months.contains('July'));
        
        //Sets are usually created from other collections like Lists       
        //Here are two methods for adding a List to a Set
        
        //1. Add an existing list when instantiating the Set
        List<ID> list0 = new List<ID>{'00Q3600000CqgXh', '00Q3600000yTEaB','00Q3600000RiGht'};
        Set<ID> setA = new Set<ID>(list0);
        
        //2. Use a Set Method to add a List (or another Set)
        List<ID> list1 = new List<ID>{'00Q3600000zUCaR', '00Q3600000QpjNq','00Q3600000RiGht'};
        setA.addAll(list1);
        
		//FIX ME! Write System Assert methods to confirm that setA contains all the elements from list0 and list1        
    }
    
    static testMethod void Maps(){
        //MAPS ARE NAMED COLLECTIONS OF DATA
        Map<String, String> fieldValues = new Map<String, String>{'Name' => '2u, Inc.', 'Website' => '2u.com', 'Phone' => '301-892-4350'};
        System.assertEquals(3, fieldValues.size());
        
        //Maps are useful to relate something you know, to something you want to know.
        //Here we map an integer (we know) to a string which holds the Mandarin word (we don't know) for the number.
        Map<Integer, String> numbers = new Map<Integer, String>();
        numbers.put(1, 'Yi');
        numbers.put(2, 'Er');
        numbers.put(3, 'San');
        
        //Notice how we use "put" instead of "add"? Same purpose, just different name.
        //See https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_methods_system_map.htm
        
        //The power of maps comes from the get() method which allows us to use the "key", something we know,
        //to get the "value", something we don't know.
        System.debug(numbers.get(1));
        
        //FIX ME! Using the data in the numbers map, uncomment the lines below and get them to pass
        //System.assertEquals('Er', numbers.get());
        //System.assertEquals(, numbers.get(3));
        
        System.debug(numbers.keySet());
        
        //FIX ME! Populate the Set called 'mynumbers' that you can then use to get the assert to pass
        Set<Integer> mynumbers;
        //System.assertEquals(numbers.keySet(),mynumbers);
        
        //FIX ME! Populate the List called 'values' that you can then use to get the assert to pass
        List<String> values;
        //System.assertEquals(numbers.values(), values);
        
        //FIX ME! On the Map Methods page in the Apex docs, find the method that allows you to remove an item from the Map
        // and get the assertion to pass.
        
        //numbers.???
        //System.assertEquals(2, numbers.size());
        
        //FIX ME! And now find and use the method to remove all the values from the Map
        // and get the assertion to pass.
        
    	//numbers.???
        //System.assert(numbers.isEmpty());
    }
}