Advanced Type Constraints
Generics: Powerful Type Constraints
Generic Type Basics
public class GenericConstraints<T extends Comparable<T>> {
private T value;
public void setValue(T value) {
this.value = value;
}
public T getMaxValue(T another) {
return (value.compareTo(another) > 0) ? value : another;
}
}
Wildcard Type Constraints
flowchart TD
A[Wildcard Types] --> B{?}
B --> C[Upper Bounded: ? extends]
B --> D[Lower Bounded: ? super]
B --> E[Unbounded: ?]
Bounded Type Parameters
public class NumericProcessor<T extends Number> {
private List<T> numbers;
public double calculateAverage() {
return numbers.stream()
.mapToDouble(Number::doubleValue)
.average()
.orElse(0.0);
}
}
Advanced Constraint Techniques
Type Constraint Comparison
Constraint Type |
Description |
Example |
Upper Bounded |
Limits type to specific superclass |
<T extends Number> |
Lower Bounded |
Allows specific parent types |
<T super Integer> |
Multiple Bounds |
Combines multiple constraints |
<T extends Comparable<T> & Serializable> |
Annotation-Based Type Constraints
@Target(ElementType.TYPE_USE)
@Retention(RetentionPolicy.RUNTIME)
public @interface NonNull {
// Custom type constraint annotation
}
public class AnnotationConstraintExample {
public void processData(@NonNull String input) {
// Enforces non-null constraint
}
}
Type Inference and Constraints
public class TypeInferenceDemo {
public static <T> List<T> createList(T... elements) {
return Arrays.asList(elements);
}
public static void main(String[] args) {
// Compiler infers type automatically
List<Integer> intList = createList(1, 2, 3, 4);
}
}
Advanced Pattern Matching
classDiagram
class TypePatternMatching {
+ matchType(Object obj)
- handleString(String s)
- handleInteger(Integer i)
}
Constraint Overhead Analysis
public class PerformanceComparison<T> {
// Demonstrates type constraint performance
public void processGeneric(T item) {
// Minimal runtime overhead
}
}
Best Practices for Type Constraints
- Use generics for type safety
- Minimize runtime type checking
- Leverage type inference
- Apply precise type bounds
- Use annotation-based constraints
LabEx Recommended Approach
- Implement type constraints strategically
- Balance between type safety and performance
- Use generics for flexible, type-safe code
By mastering advanced type constraints, developers can create more robust, type-safe, and efficient Java applications with LabEx's cutting-edge programming techniques.