XML has two elements when getting length but null pointer exception when trying to access and append the node

<DG1root>
<DG1>
    <DG1.1>1</DG1.1>
    <DG1.4>he he he</DG1.4>
    <DG1.5>20141128</DG1.5>
    <DG1.6>Admitting</DG1.6>
    <DG1.15>1</DG1.15>
    <DG1.16>
        <XCN.1>1</XCN.1>
        <XCN.2>Nanayakkara</XCN.2>
        <XCN.3>Nanayakkara</XCN.3>
        <XCN.4>Doctor of Medicine (M.D.)</XCN.4>
    </DG1.16>
    <DG1.17>Medication</DG1.17>
</DG1>
<DG1>
    <DG1.1>2</DG1.1>
    <DG1.4>heeeeeeee</DG1.4>
    <DG1.5>20141128</DG1.5>
    <DG1.6>Working</DG1.6>
    <DG1.15>0</DG1.15>
    <DG1.16>
        <XCN.1>1</XCN.1>
        <XCN.2>Nanayakkara</XCN.2>
        <XCN.3>Nanayakkara</XCN.3>
        <XCN.4>Doctor of Medicine (M.D.)</XCN.4>
    </DG1.16>
    <DG1.17>Other</DG1.17>
    </DG1>
</DG1root>

after

NodeList listDG1 = symptomAndDiagnosisDoc.getElementsByTagName("DG1root")
                                         .item(0).getChildNodes();

listDG1.getLength()     

gives the length of 2. but when i try to append it to a new root, after

Node root = symptomAndDiagnosisDoc.importNode(
                    patientDoc.getElementsByTagName("ADT_A04").item(0),true);

which symptomAndDiagnsisDoc contains the above xml,

for (int i=0; i<listDG1.getLength(); i++){
  root.appendChild(listDG1.item(i));
}

this only append one DG1 element but not the other. I only want to append the DG1 elements.

Please be kind enough to explain what im doing wrong here. Thank you :)