rest-assured/src/main/java/io/restassured/internal/http/HTTPBuilder.java
public void setHeaders(Map<?, ?> headers) {
        this.defaultRequestHeaders.clear();
        if (headers == null) return;
        for (Object key : headers.keySet()) {
            Object val = headers.get(key);
            if (val == null) continue;
            this.defaultRequestHeaders.put(key.toString(), val.toString());
        }
    }
public void setHeaders(Map<?, ?> headers) {
        this.defaultRequestHeaders.clear();
        if (headers == null) return;
        for (Object key : headers.keySet()) {
            Object val = headers.get(key);
            if (val == null) continue;
            this.defaultRequestHeaders.put(key.toString(), val.toString());
        }
    }
Set the default headers to add to all requests made by this builder
instance.  These values will replace any previously set default headers.

@param headers map of header names & values.