Recibo una larga lista de errores. ¿Alguien puede sugerirme dónde me estoy equivocando?GroupLayout.

layout.setHorizontalGroup(
    layout.createSequentialGroup()
        .addComponent(new JLabel("Enter Book Name"))
        .addComponent(new JTextField("TextField", 20))
);

Error:

    Exception in thread "main" java.lang.IllegalStateException:
        javax.swing.JTextField[,0,0,0x0,invalid,layout=javax.swing.
            plaf.basic.BasicTextUI$UpdateHandler,alignmentX=0.0,
            alignmentY=0.0,border=javax.swing.plaf.BorderUIResource$
            CompoundBorderUIResource@3d0bbf9e,flags=296,maximumSize=,
            minimumSize=,preferredSize=,caretColor=sun.swing.
            PrintColorUIResource[r=51,g=51,b=51],disabledTextColor=javax
            .swing.plaf.ColorUIResource[r=184,g=207,b=229],editable=true
            ,margin=javax.swing.plaf.InsetsUIResource[top=0,left=0,
            bottom=0,right=0],selectedTextColor=sun.swing.
            PrintColorUIResource[r=51,g=51,b=51],selectionColor=javax.
            swing.plaf.ColorUIResource[r=184,g=207,b=229],columns=20,
            columnWidth=0,command=,horizontalAlignment=LEADING]
            is not attached to a vertical group
            at javax.swing.GroupLayout.checkComponents(Unknown Source)
            at javax.swing.GroupLayout.prepare(Unknown Source)