JavaSearchByClassType.java

package com.company;

import java.util.ArrayList;
import java.util.concurrent.ThreadLocalRandom;
import java.util.stream.Collectors;

public class JavaSearchByClassType {
    public static void main(String[] args) {
        ArrayList<Object> objects = new ArrayList<>();
        // запихиваем всякого
        for (int i = 0; i < 5; i++){
            objects.add(Math.random());
            objects.add((char)(ThreadLocalRandom.current().nextInt(25) + 65));
        }
        System.out.println("Doubles: ");
        ArrayList<Double> doubles = findByClass(objects, Double.class);
        for (int i = 0; i < doubles.size(); i++)
            System.out.println(doubles.get(i).getClass() + " " + doubles.get(i));

        System.out.println("Characters:");
        ArrayList<Character> characters = findByClass(objects, Character.class);
        for (int i = 0; i < characters.size(); i++)
            System.out.println(characters.get(i).getClass() + " " + characters.get(i));
    }
    private static <classType> ArrayList<classType> findByClass(ArrayList<?> list, Class<?> classType){
        return (ArrayList<classType>) list.stream().filter(obj -> obj.getClass() == classType).map(classType::cast).collect(Collectors.toList());
    }
}
//Doubles:
//class java.lang.Double 0.7098515510570728
//class java.lang.Double 0.05707583089905499
//class java.lang.Double 0.7872549851678237
//class java.lang.Double 0.8752028316550686
//class java.lang.Double 0.408371159251227
//        Characters:
//class java.lang.Character I
//class java.lang.Character E
//class java.lang.Character H
//class java.lang.Character R
//class java.lang.Character P