dyong0/TemplateEvaluator.java

## TemplateEvaluator.java
import java.util.HashMap;
import java.util.Map;
import java.util.function.Supplier;

public class TemplateEvaluator {
	private Map<String, Supplier<String>> keywords = new HashMap<>();

	public void addTemplateVariable(String keyword, Supplier<String> template) {
		keywords.put(keyword, template);
	}

	public String evaluteTemplate(String template) {
		StringBuilder sbTemplate = new StringBuilder();
		int prevIndex = 0;
		int index = nextIndex(prevIndex, template);

		while (index > -1) {
			sbTemplate.append(template.substring(0, index));
			template = template.substring(index);

			index = template.indexOf("}");
			String keyword = template.substring(2, index);
			sbTemplate.append(keywords.get(keyword).get());

			template = template.substring(index + 1);

			index = template.indexOf("${");
		}
		sbTemplate.append(template);

		return sbTemplate.toString();
	}

	private int nextIndex(int index, String template) {
		return template.indexOf("${", index);
	}
}

## TemplateEvaluatorTest.java
import static org.junit.Assert.assertEquals;

import java.time.LocalDate;

import org.junit.Before;
import org.junit.Test;

public class TemplateEvaluatorTest {
	private TemplateEvaluator evaluator;

	@Before
	public void setup(){
		evaluator = new TemplateEvaluator();

		evaluator.addTemplateVariable("today", () -> LocalDate.now().toString());
		evaluator.addTemplateVariable("year", () -> String.valueOf(LocalDate.now().getYear()));
		evaluator.addTemplateVariable("month", () -> String.valueOf(LocalDate.now().getMonthValue() + 1));

		evaluator.addTemplateVariable("day", () -> String.valueOf(LocalDate.now().getDayOfMonth()));
	}

	@Test
	public void testTemplate(){
		assertEquals(evaluator.evaluteTemplate("<html>${today}</html>"), "<html>" + LocalDate.now().toString() + "</html>");
	}
}
	import java.util.HashMap;
	import java.util.Map;
	import java.util.function.Supplier;

	public class TemplateEvaluator {
	private Map<String, Supplier<String>> keywords = new HashMap<>();

	public void addTemplateVariable(String keyword, Supplier<String> template) {
	keywords.put(keyword, template);
	}

	public String evaluteTemplate(String template) {
	StringBuilder sbTemplate = new StringBuilder();
	int prevIndex = 0;
	int index = nextIndex(prevIndex, template);

	while (index > -1) {
	sbTemplate.append(template.substring(0, index));
	template = template.substring(index);

	index = template.indexOf("}");
	String keyword = template.substring(2, index);
	sbTemplate.append(keywords.get(keyword).get());

	template = template.substring(index + 1);

	index = template.indexOf("${");
	}
	sbTemplate.append(template);

	return sbTemplate.toString();
	}

	private int nextIndex(int index, String template) {
	return template.indexOf("${", index);
	}
	}
	import static org.junit.Assert.assertEquals;

	import java.time.LocalDate;

	import org.junit.Before;
	import org.junit.Test;

	public class TemplateEvaluatorTest {
	private TemplateEvaluator evaluator;

	@Before
	public void setup(){
	evaluator = new TemplateEvaluator();

	evaluator.addTemplateVariable("today", () -> LocalDate.now().toString());
	evaluator.addTemplateVariable("year", () -> String.valueOf(LocalDate.now().getYear()));
	evaluator.addTemplateVariable("month", () -> String.valueOf(LocalDate.now().getMonthValue() + 1));

	evaluator.addTemplateVariable("day", () -> String.valueOf(LocalDate.now().getDayOfMonth()));
	}

	@Test
	public void testTemplate(){
	assertEquals(evaluator.evaluteTemplate("<html>${today}</html>"), "<html>" + LocalDate.now().toString() + "</html>");
	}
	}