Why do I get a compiler error in this code ? How do I fix it ?
public class Container<T> {
private T content;
private T defaultValue;
public <T> Container(T defaultValue){
//Compiler error - incompatible types: T cannot be converted to T.
this.defaultValue = defaultValue;
}
}
After type erasure, T defaultValue would become Object defaultValue. Then why can't we assign T defaultValue to Object defaultValue ? After all, every type in Java is an Object.
Remove the <T> from in front of the constructor. Java thinks you are trying to create a new generic. It thinks the T you have in the class statement is a different T then you have in the constructor. In Java's eyes you have T1 and T2. You are trying to assign T2 to a T1 variables. Even though they may be identical in methods, inheritance, etc... they are two distinct generics.
This is how Java interprets what you've written.
public class Container<T1> {
private T1 content;
private T1 defaultValue;
public <T2> Container(T2 defaultValue){
//Compiler error - incompatible types: T cannot be converted to T.
this.defaultValue = defaultValue;
}
}
What you meant to write was this. You don't need to specify T inside < > anywhere since it's included in the class syntax.
public class Container<T> {
private T content;
private T defaultValue;
public Container(T defaultValue){
this.defaultValue = defaultValue;
}
}