config/src/main/java/org/springframework/security/config/annotation/web/configurers/HeadersConfigurer.java
private List<HeaderWriter> getHeaderWriters() {
		List<HeaderWriter> writers = new ArrayList<>();
		addIfNotNull(writers, contentTypeOptions.writer);
		addIfNotNull(writers, xssProtection.writer);
		addIfNotNull(writers, cacheControl.writer);
		addIfNotNull(writers, hsts.writer);
		addIfNotNull(writers, frameOptions.writer);
		addIfNotNull(writers, hpkp.writer);
		addIfNotNull(writers, contentSecurityPolicy.writer);
		addIfNotNull(writers, referrerPolicy.writer);
		addIfNotNull(writers, featurePolicy.writer);
		writers.addAll(headerWriters);
		return writers;
	}
private List<HeaderWriter> getHeaderWriters() {
		List<HeaderWriter> writers = new ArrayList<>();
		addIfNotNull(writers, contentTypeOptions.writer);
		addIfNotNull(writers, xssProtection.writer);
		addIfNotNull(writers, cacheControl.writer);
		addIfNotNull(writers, hsts.writer);
		addIfNotNull(writers, frameOptions.writer);
		addIfNotNull(writers, hpkp.writer);
		addIfNotNull(writers, contentSecurityPolicy.writer);
		addIfNotNull(writers, referrerPolicy.writer);
		addIfNotNull(writers, featurePolicy.writer);
		writers.addAll(headerWriters);
		return writers;
	}
Gets the {@link HeaderWriter} instances and possibly initializes with the defaults.

@return