Simple Tag and Builder

Tag.java

import java.io.IOException;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Map;

public class Tag {

    private final String tagName;
    private Map<String, String> attributes;
    private String text;
    private List<Tag> children;

    Tag(String tagName) {
        this.tagName = tagName;
    }

    public String getTagName() {
        return tagName;
    }

    public Map<String, String> getAttributes() {
        return attributes == null ? Collections.emptyMap() : Collections.unmodifiableMap(attributes);
    }

    void setAttributes(Map<String, String> attributes) {
        this.attributes = attributes;
    }

    public String getText() {
        return text;
    }

    void setText(String text) {
        this.text = text;
    }

    public List<Tag> getChildren() {
        return children == null ? Collections.emptyList() : Collections.unmodifiableList(children);
    }

    public Tag append(Tag child) {
        if (children == null) {
            children = new ArrayList<>();
        }
        children.add(child);
        return this;
    }

    public void write(OutputStream stream) throws IOException {
        stream.write(String.format("<%s", tagName).getBytes());
        for (Map.Entry<String, String> attr : getAttributes().entrySet()) {
            stream.write(String.format(" %s=\"%s\"", attr.getKey(), attr.getValue()).getBytes());
        }
        stream.write(">".getBytes());
        if (text != null) {
            stream.write(text.getBytes());
        }
        for (Tag child : getChildren()) {
            child.write(stream);
        }
        stream.write(String.format("</%s>", tagName).getBytes());
    }

}

TagBuilder.java

import java.util.HashMap;
import java.util.Map;

public class TagBuilder {

    private final String tagName;
    private Map<String, String> attributes;
    private String text;

    public TagBuilder(String tagName) {
        this.tagName = tagName;
    }

    public TagBuilder attribute(String name, String value) {
        attributes(new HashMap<String, String>() {
            {
                put(name, value);
            }
        });
        return this;
    }

    public TagBuilder attributes(Map<String, String> attributes) {
        if (this.attributes == null) {
            this.attributes = new HashMap<>();
        }
        this.attributes.putAll(attributes);
        return this;
    }

    public TagBuilder text(String text) {
        this.text = text;
        return this;
    }

    public Tag build() {
        Tag tag = new Tag(tagName);
        if (attributes != null && !attributes.isEmpty()) {
            tag.setAttributes(attributes);
        }
        if (text != null) {
            tag.setText(text);
        }
        return tag;
    }

}