Java Generics Tutorial
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- Java Generics - No Cast
- Java Generics - No Static field
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- Java Generics - No Primitive Types
- Java Generics - Methods Erasure
- Unbounded Types Erasure
- Java Generics - Bound Types Erasure
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- Generics - Guidelines for Wildcards
- Lower Bounded Wildcards
- Generics - Unbounded Wildcards
- Upper Bounded Wildcards
- Java Generics - Generic Map
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- Bounded Type Parameters
- Java Generics - Raw Types
- Java Generics - Parameterized Types
- Java Generics - Multiple Type
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- Java Generics - Type inference
- Type Parameter Naming Conventions
- Java Generics - Generic Classes
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- Java Generics - Overview
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Generics - Unbounded Wildcards
Java Generics - Unbounded Wildcards
The question mark (?), represents the wildcard, stands for unknown type in generics. There may be times when any object can be used when a method can be implemented using functionapty provided in the Object class or When the code is independent of the type parameter.
To declare a Unbounded Wildcard parameter, pst the ? only.
Example
Following example illustrates how extends is used to specify an unbounded wildcard.
package com.tutorialspoint;
import java.util.Arrays;
import java.util.List;
pubpc class GenericsTester {
pubpc static void printAll(List<?> pst) {
for (Object item : pst)
System.out.println(item + " ");
}
pubpc static void main(String args[]) {
List<Integer> integerList = Arrays.asList(1, 2, 3);
printAll(integerList);
List<Double> doubleList = Arrays.asList(1.2, 2.3, 3.5);
printAll(doubleList);
}
}
This will produce the following result −
Output
1 2 3 1.2 2.3 3.5Advertisements