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copied!<p>Before I talk about the difference between a Pair and a HashMap, let me tell you why that's not really the question you want answered. What you really want to know is why would you take an Object and break it into a list of key/value primitivies.</p> <p>The code you are referencing is converting from an object oriented approach of using a class <code>Patient</code> (which really looks like it should be called <code>PatientInfo</code>) into a list of primitives, they are essentialy "deObjectOrienting" the class.</p> <p>So in their model each class variable becomes a <code>Pair</code> where the variable name become the key, and the variable value become the value.</p> <p>Here is an expanded example class</p> <pre><code>// Old style (Object oriented) class PatientInfo{ String religion; String address; } PatientInfo patientInfo = new PatientInfo(); patientInfo.setReligion("myReligionName"); patientInfo.setAddress("address of the patient"); // New Style, key/value primitive pairs (very not object oriented) Pair<String,String> religionInfo = new Pair<String,String>("religion","myReligionName"); Pair<String,String> addressInfo = new Pair<String,String>("address","address of the patient"); </code></pre> <p>They then add these either the <code>Patient</code> or the <code>Pair</code> into a List.</p> <p>Why would someone do this is a good question. Most people try to become more object oriented as it makes coding easier. Perhaps since it's only a single variable in the Clss they figured why not remove the class entirely?</p> <p>To your original question between a Pair and a HashMap. A Pair is just a key/value. A HashMap is the collection usually used to store many key/value pairs. Here they are using a List where they should probably be using the HashMap.</p>

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