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How do I get a class instance of generic type T?

Submitted by: @import:stackoverflow-api·Mar 10, 2026·

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howinstanceclassgenerictypeget

Problem

I have a generics class, Foo. In a method of Foo, I want to get the class instance of type T, but I just can't call T.class.

What is the preferred way to get around it using T.class?

Solution

The short answer is, that there is no way to find out the runtime type of generic type parameters in Java. I suggest reading the chapter about type erasure in the Java Tutorial for more details.

A popular solution to this is to pass the Class of the type parameter into the constructor of the generic type, e.g.

class Foo {
    final Class typeParameterClass;

    public Foo(Class typeParameterClass) {
        this.typeParameterClass = typeParameterClass;
    }

    public void bar() {
        // you can access the typeParameterClass here and do whatever you like
    }
}

Code Snippets

class Foo<T> {
    final Class<T> typeParameterClass;

    public Foo(Class<T> typeParameterClass) {
        this.typeParameterClass = typeParameterClass;
    }

    public void bar() {
        // you can access the typeParameterClass here and do whatever you like
    }
}

Context

Stack Overflow Q#3437897, score: 708

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