public void appendToString(StringBuffer buffer, String toString) {
        if (toString != null) {
            int pos1 = toString.indexOf(contentStart) + contentStart.length();
            int pos2 = toString.lastIndexOf(contentEnd);
            if (pos1 != pos2 && pos1 >= 0 && pos2 >= 0) {
                String data = toString.substring(pos1, pos2);
                if (fieldSeparatorAtStart) {
                    removeLastFieldSeparator(buffer);
                }
                buffer.append(data);
                appendFieldSeparator(buffer);
            }
        }
    }
<p>Append to the <code>toString</code> another toString.</p>
<p>NOTE: It assumes that the toString has been created from the same ToStringStyle. </p>

<p>A <code>null</code> <code>toString</code> is ignored.</p>

@param buffer  the <code>StringBuffer</code> to populate
@param toString  the additional <code>toString</code>
@since 2.0
android/android_framework/base/src/main/java/lang3/builder/ToStringStyle.java