class PDPushButton extends PDButton
{
    /**
     * @see PDField#PDField(PDAcroForm)
     *
     * @param acroForm The acroform.
     */
    public PDPushButton(PDAcroForm acroForm)
    {
        super(acroForm);
        getCOSObject().setFlag(COSName.FF, FLAG_PUSHBUTTON, true);
    }
    
    /**
     * Constructor.
     * 
     * @param acroForm The form that this field is part of.
     * @param field the PDF object to represent as a field.
     * @param parent the parent node of the node
     */
    PDPushButton(PDAcroForm acroForm, COSDictionary field, PDNonTerminalField parent)
    {
        super(acroForm, field, parent);
    }

    @Override
    public List<String> getExportValues()
    {
        return Collections.emptyList();
    }
    
    @Override
    public void setExportValues(List<String> values)
    {<FILL_FUNCTION_BODY>}
    
    @Override
    public String getValue()
    {
        return "";
    }

    @Override
    public String getDefaultValue()
    {
        return "";
    }

    @Override
    public String getValueAsString()
    {
        return getValue();
    }

    @Override
    public Set<String> getOnValues()
    {
        return Collections.emptySet();
    }

    @Override
    void constructAppearances() throws IOException
    {
        // TODO: add appearance handler to generate/update appearance
    } 
}

        if (values != null && !values.isEmpty())
        {
            throw new IllegalArgumentException("A PDPushButton shall not use the Opt entry in the field dictionary");
        }
    
<methods>public java.lang.String getDefaultValue() ,public List<java.lang.String> getExportValues() ,public Set<java.lang.String> getOnValues() ,public java.lang.String getValue() ,public java.lang.String getValueAsString() ,public boolean isPushButton() ,public boolean isRadioButton() ,public void setDefaultValue(java.lang.String) ,public void setExportValues(List<java.lang.String>) ,public void setValue(java.lang.String) throws java.io.IOException,public void setValue(int) throws java.io.IOException<variables>static final int FLAG_PUSHBUTTON,static final int FLAG_RADIO,static final int FLAG_RADIOS_IN_UNISON