public static Header getMergedMetricsHeader(List<File> inputMetricsList, File outputMetrics) {
    List<String> header = new ArrayList<>();
    for (File file : inputMetricsList)
        header.add("INPUT="+ file.getAbsolutePath());
    header.add("OUTPUT="+ outputMetrics.getAbsolutePath());

    return new StringHeader(StringUtils.join(header, "\t"));
}
 

public void writeHistograms() {
    for (final String sample : samples) {
        final MetricsFile<?, Integer> refMetricsFile = new MetricsFile<>();
        refMetricsFile.addHeader(new StringHeader(sample));
        refSiteHistograms.get(sample).values().forEach(refMetricsFile::addHistogram);
        refMetricsFile.write(new File(tmpDir,IOUtils.urlEncode(sample) + REF_HIST_EXTENSION));

        final MetricsFile<?, Integer> altMetricsFile = new MetricsFile<>();
        altMetricsFile.addHeader(new StringHeader(sample));
        depthOneAltHistograms.get(sample).getHistograms().forEach(altMetricsFile::addHistogram);
        altMetricsFile.write(new File(tmpDir, IOUtils.urlEncode(sample) + ALT_HIST_EXTENSION));

    }
}