public void add(String name, String value) {
        if (name == null) throw new NullPointerException("name == null");
        if (name.isEmpty()) throw new IllegalArgumentException("name is empty");
        if (value == null) throw new NullPointerException("value == null");

        if (mHeaderMap == null) {
            mHeaderMap = new HashMap<>();
        }

        List<String> values = mHeaderMap.get(name);
        if (values == null) {
            values = new ArrayList<>();
            mHeaderMap.put(name, values);
        }

        if (!values.contains(value)) {
            values.add(value);
        }
    }
public void add(String name, String value) {
        if (name == null) throw new NullPointerException("name == null");
        if (name.isEmpty()) throw new IllegalArgumentException("name is empty");
        if (value == null) throw new NullPointerException("value == null");

        if (mHeaderMap == null) {
            mHeaderMap = new HashMap<>();
        }

        List<String> values = mHeaderMap.get(name);
        if (values == null) {
            values = new ArrayList<>();
            mHeaderMap.put(name, values);
        }

        if (!values.contains(value)) {
            values.add(value);
        }
    }
public void add ( String name , String value ) { if ( name == null ) throw new NullPointerException ( "name == null" ) ; if ( name . isEmpty ( ) ) throw new IllegalArgumentException ( "name is empty" ) ; if ( value == null ) throw new NullPointerException ( "value == null" ) ; if ( mHeaderMap == null ) { mHeaderMap = new HashMap <> ( ) ; } List < String > values = mHeaderMap . get ( name ) ; if ( values == null ) { values = new ArrayList <> ( ) ; mHeaderMap . put ( name , values ) ; } if ( ! values . contains ( value ) ) { values . add ( value ) ; } }
We have already handled etag, and will add 'If-Match' & 'Range' value if it works.

@see com.liulishuo.filedownloader.download.ConnectTask#addUserRequiredHeader
We have already handled etag and will add If - Match & Range value if it works .