Applying Generics

Applying Generics Writing Type-Safe Code

Generic Class or Interface ,[object Object],[object Object],[object Object],class X<T1,T2> { private T1 ref1; private T2 ref2; public X(T1 ref1,T2 ref2) { this.ref1 = ref1; this.ref2 = ref2; } public T1 getRef1() { return ref1; } public T2 getRef2() { return ref2; } }

Primary purpose of Java generics ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Prime Benefit ,[object Object],[object Object],[object Object],What’s the meaning of Type-safety?

SubTyping & WildCards ,[object Object],[object Object],[object Object]

Subtyping and the Substitution Principle ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Substitution Principle contd. ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Substitution Principle contd. ,[object Object],[object Object],[object Object]

Bounded Type Parameter ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],public static void main(String[] args) { Integer ints[] = {7,8,5}; Double d[] = {5.3,7.44,6.008}; Float f[] = {4.3f,1.2f,2.3f}; GenTest<Integer> ref1 = new GenTest<Integer>(ints); GenTest<Double> ref2 = new GenTest<Double>(d); GenTest<Float> ref3 = new GenTest<Float>(f); ref1.sum(); ref2.sum(); ref3.sum(); }

WildCard (?) ,[object Object],[object Object],[object Object],[object Object],[object Object]

Using ? extends T ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Using ? extends T contd. ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Using ? extends T contd. ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Always Remember if a structure contains elements with a type of the form ? extends E, we can get elements out of the structure, but we cannot put elements into the structure.

? super T ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

? super T contd. ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Get & Put Principle ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Are the following code snippets correct? ,[object Object],[object Object],[object Object],[object Object],[object Object],ArrayList<Number> i; i = new ArrayList<Number>(); i.add(6.7); i.add(89); ArrayList<? super Integer> al = i; Test your understanding Is ArrayList<String> and ArrayList<? extends String> same?

Comparison of Arrays & Lists ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Comparison & Bounds ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Maximum of a Collection ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Applying Generics

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