Java 8 | Writing custom Stream API using builder pattern

In this post we are going to create simple Java 8 Stream API using builder pattern. Check builder pattern post here. 

API will provide below four methods -

1. sort - Sort the list
2. limit - Fetch only N numbers from the list
3. distinct - Remove duplicates from the list
4. forEach - Print the list

	import java.util.ArrayList;
	import java.util.List;
	import java.util.Collections;
	import java.lang.Integer;
	interface CustomStreamApi<U extends Comparable> {
	CustomStreamApi<U> sort();
	CustomStreamApi<U> limit(long size);
	CustomStreamApi<U> distinct();
	void forEach();
	}
	public class CustomStream<T extends Comparable> implements CustomStreamApi<T> {
	private List<T> list;
	CustomStream(List<T> list) {
	this.list = list;
	}
	@Override
	public void forEach() {
	for(T t : this.list) {
	System.out.println(t);
	}
	}
	@Override
	public CustomStream sort() {
	Collections.sort(this.list);
	return this;
	}
	@Override
	public CustomStream limit(long size) {
	List<T> newList = new ArrayList<>();
	int count = 0;
	for(T integer : this.list) {
	if(count > size) {
	break;
	}
	newList.add(integer);
	count++;
	}
	this.list = newList;
	return this;
	}
	@Override
	public CustomStream distinct() {
	List<T> newList = new ArrayList<>();
	for(T integer : this.list) {
	if(newList.contains(integer)) {
	continue;
	}
	newList.add(integer);
	}
	this.list = newList;
	return this;
	}
	@Override
	public String toString() {
	final StringBuffer sb = new StringBuffer("CustomStream{");
	sb.append("list=").append(list);
	sb.append('}');
	return sb.toString();
	}
	public static <T extends Comparable> CustomStream stream(List<T> integerList) {
	return new CustomStream(integerList);
	}
	public static void main(String[] args) {
	List<Integer> integers = new ArrayList<>();
	integers.add(1);
	integers.add(2);
	integers.add(1);
	integers.add(5);
	integers.add(5);
	integers.add(6);
	integers.add(4);
	integers.add(0);
	CustomStream.stream(integers).sort().distinct().limit(3).forEach();
	List<Double> doubles = new ArrayList<>();
	doubles.add(1.1);
	doubles.add(2.1);
	doubles.add(1.1);
	doubles.add(5.1);
	doubles.add(5.1);
	doubles.add(6.1);
	doubles.add(4.1);
	doubles.add(0.1);
	CustomStream.stream(doubles).sort().distinct().limit(3).forEach();
	}
	}

view raw CustomStream.java hosted with ❤ by GitHub