A utility class to build comma separated lists.

CommaStringBuilder

public class CommaStringBuilder implements Appendable {
    private final StringBuilder sb;
    private boolean first = true;

    public CommaStringBuilder() {
        sb = new StringBuilder();
    }

    public CommaStringBuilder(String s) {
        sb = new StringBuilder(s);
    }

    public CommaStringBuilder(StringBuilder sb) {
        this.sb = sb;
    }

    public CommaStringBuilder add(String s) {
        if (first)
            first = false;
        else
            sb.append(",");
        sb.append(s);
        return this;
    }

    public CommaStringBuilder add(Object x) {
        return add(x.toString());
    }

    public CommaStringBuilder add(long i) {
        if (first)
            first = false;
        else
            sb.append(",");
        sb.append(i);
        return this;
    }

    @Override
    public CommaStringBuilder append(CharSequence s) {
        sb.append(s);
        return this;
    }

    @Override
    public CommaStringBuilder append(CharSequence csq, int start, int end) {
        sb.append(csq, start, end);
        return this;
    }

    @Override
    public CommaStringBuilder append(char c) {
        sb.append(c);
        return this;
    }

    public CommaStringBuilder append(Object x) {
        sb.append(x);
        return this;
    }

    public CommaStringBuilder append(long i) {
        sb.append(i);
        return this;
    }

    public void clear() {
        sb.setLength(0);
        first = true;
    }

    @Override
    public String toString() {
        return sb.toString();
    }

}