Generate number, character, strings, boolean and dates for test data using strategy design pattern.

GeneratorTest.java

import java.time.Instant;
import java.time.LocalDate;
import java.time.ZoneId;
import java.util.Random;

interface Generator<T> {
    T generate();
    static Generator<Boolean> generateBoolean(){
        return new Generator<>() {
            Random random = new Random();
            @Override
            public Boolean generate() {
                return random.nextBoolean();
            }
        };
    }
    static Generator<Integer> generateNumber(){
        return () -> new Random().nextInt(100000);
    }
    static Generator<Character> generateCharacter(){
        return new Generator<>() {
            Random random = new Random();
            char[] chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ".toCharArray();
            @Override
            public Character generate() {
                return chars[random.nextInt(chars.length)];
            }
        };
    }
    static Generator<String> generateString(){
        return () -> {
            char[] chars = new char[7];
            Generator<Character> generator = generateCharacter();
            for(int i=0; i<7; i++){
                chars[i] = generator.generate();
            }
            return new String(chars);
        };
    }
    static Generator<LocalDate> generateDate(){
        return () -> {
            // Number of seconds from 1970 Jan 1 to 2018 Dec 31 is 1546214400.
            int instance = new Random().nextInt(1546214400);
            return LocalDate.ofInstant(Instant.ofEpochSecond(instance), ZoneId.systemDefault());
        };
    }
}

class GeneratorTest{
    public static void main(String[] args) {
        testGenerator(Generator.generateNumber());
        testGenerator(Generator.generateBoolean());
        testGenerator(Generator.generateCharacter());
        testGenerator(Generator.generateString());
        testGenerator(Generator.generateDate());
    }
    private static void testGenerator(Generator<? extends Comparable> gen){
        for(int i=0; i< 5;i++)
            System.out.print(gen.generate()+" ");
        System.out.println();
    }
}