Source: https://docs.google.com/presentation/d/1npWOehaHb9Gke5pjywR0unLIJM9XfWr5/edit#slide=id.p47
Lists with sentinel (dummy) node
- Dummy nodes are Nodes whose data fields are always null – they contain no data from the “user”.
- The dummy nodes will always exist, even if the user hasn’t added any data yet.
- Head will never points to null
- These nodes will simplify the implementation for certain methods.
- No need to check if the list is empty.
Generic Types
Allow us to have null as a data value.
int vs. Integer
- Generic types must be reference types. You cannot replace a generic type with a primitive type such as int or char.
- For example, the following statement is wrong:
ArrayList<int> intList = new ArrayList<int>();- To create an ArrayList object for int values, you have to use:
ArrayList<Integer> intList = new ArrayList<Integer>();- You can add an int value to intList by creating a new object of type Integer. For example,
intList.add(new Integer(5));- Another way: You can add an int value to intList. For example,
intList.add(5);- Java automatically wraps 5 into new Integer(5). This is called autoboxing
Diamond Operator <>
- Before JDK 7: Explicitly specifying generic class’s instantiation parameter type.
ArrayList<String> list = new ArrayList<String>();- After JDK 7:
ArrayList<String> list = new ArrayList<>();