get Element Type Of List - Java Reflection

Java examples for Reflection:Type

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Description

get Element Type Of List

Demo Code


//package com.java2s;

import java.lang.reflect.GenericArrayType;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;

import java.util.List;

public class Main {
    public static Type getElementTypeOfList(final Type type) {
        if (!isTypeOf(type, List.class)) {
            return null;
        }//from w  ww  .j av  a 2 s .c o m
        return getGenericParameter(type, 0);
    }

    public static boolean isTypeOf(final Type type, final Class<?> clazz) {
        if (Class.class.isInstance(type)) {
            return clazz.isAssignableFrom(Class.class.cast(type));
        }
        if (ParameterizedType.class.isInstance(type)) {
            final ParameterizedType parameterizedType = ParameterizedType.class
                    .cast(type);
            return isTypeOf(parameterizedType.getRawType(), clazz);
        }
        return false;
    }

    public static Type[] getGenericParameter(final Type type) {
        if (ParameterizedType.class.isInstance(type)) {
            return ParameterizedType.class.cast(type)
                    .getActualTypeArguments();
        }
        if (GenericArrayType.class.isInstance(type)) {
            return getGenericParameter(GenericArrayType.class.cast(type)
                    .getGenericComponentType());
        }
        return null;
    }

    public static Type getGenericParameter(final Type type, final int index) {
        if (!ParameterizedType.class.isInstance(type)) {
            return null;
        }
        final Type[] genericParameter = getGenericParameter(type);
        if (genericParameter == null) {
            return null;
        }
        return genericParameter[index];
    }
}

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