Java Generics Tutorial
Selected Reading
- Java Generics - Discussion
- Java Generics - Useful Resources
- Java Generics - Quick Guide
- Java Generics - No Overload
- Java Generics - No Exception
- Java Generics - No Array
- Java Generics - No instanceOf
- Java Generics - No Cast
- Java Generics - No Static field
- Java Generics - No Instance
- Java Generics - No Primitive Types
- Java Generics - Methods Erasure
- Unbounded Types Erasure
- Java Generics - Bound Types Erasure
- Java Generics - Types Erasure
- Generics - Guidelines for Wildcards
- Lower Bounded Wildcards
- Generics - Unbounded Wildcards
- Upper Bounded Wildcards
- Java Generics - Generic Map
- Java Generics - Generic Set
- Java Generics - Generic List
- Java Generics - Multiple Bounds
- Bounded Type Parameters
- Java Generics - Raw Types
- Java Generics - Parameterized Types
- Java Generics - Multiple Type
- Java Generics - Generic Methods
- Java Generics - Type inference
- Type Parameter Naming Conventions
- Java Generics - Generic Classes
- Java Generics - Environment Setup
- Java Generics - Overview
- Java Generics - Home
Selected Reading
- Who is Who
- Computer Glossary
- HR Interview Questions
- Effective Resume Writing
- Questions and Answers
- UPSC IAS Exams Notes
Bounded Type Parameters
Java Generics - Bounded Type Parameters
There may be times when you ll want to restrict the kinds of types that are allowed to be passed to a type parameter. For example, a method that operates on numbers might only want to accept instances of Number or its subclasses. This is what bounded type parameters are for.
To declare a bounded type parameter, pst the type parameter s name, followed by the extends keyword, followed by its upper bound.
Example
Following example illustrates how extends is used in a general sense to mean either "extends" (as in classes) or "implements" (as in interfaces). This example is Generic method to return the largest of three Comparable objects −
pubpc class MaximumTest {
// determines the largest of three Comparable objects
pubpc static <T extends Comparable<T>> T maximum(T x, T y, T z) {
T max = x; // assume x is initially the largest
if(y.compareTo(max) > 0) {
max = y; // y is the largest so far
}
if(z.compareTo(max) > 0) {
max = z; // z is the largest now
}
return max; // returns the largest object
}
pubpc static void main(String args[]) {
System.out.printf("Max of %d, %d and %d is %d
",
3, 4, 5, maximum( 3, 4, 5 ));
System.out.printf("Max of %.1f,%.1f and %.1f is %.1f
",
6.6, 8.8, 7.7, maximum( 6.6, 8.8, 7.7 ));
System.out.printf("Max of %s, %s and %s is %s
","pear",
"apple", "orange", maximum("pear", "apple", "orange"));
}
}
This will produce the following result −
Output
Max of 3, 4 and 5 is 5 Max of 6.6,8.8 and 7.7 is 8.8 Max of pear, apple and orange is pearAdvertisements