How to remove child element from XML in java?

问题:

This is my XML file

<?xml version="1.0" encoding ="utf-8" ?>
<mcss>
    <quest ans="1"> 
        <question><![CDATA[Write 5x= 3y-1 as linear equation form.]]></question>
        <options>
            <option><![CDATA[5x-3y+1=0]]></option>
            <option><![CDATA[-5x-3y-1=0]]></option>
            <option><![CDATA[5x+3y+1=0]]></option>          
        </options>
        <explaination><![CDATA[Recall the linear equation in two variables form.]]></explaination>
    </quest>
</mcss>

I just want to remove 2nd one option from my xml.
My java code remove all option from my options element. by using option.getParentElement().removeChild("option");

try {
    String path="D://test//n2027_set1.xml";
    File structureXml = new File(path);
    SAXBuilder saxb = new SAXBuilder();
    Document document = saxb.build(structureXml);
    Element rootElement = document.getRootElement();
    XMLOutputter xmlOutput = new XMLOutputter();

    List qestList = rootElement.getChildren();
    for (int i = 0; i < qestList.size(); i++) {
        Element quesList = (Element) qestList.get(i);
        System.out.println(quesList.getAttributeValue("ans"));
        //change ans field
        quesList.setAttribute("ans", ""+i);
        List qList = quesList.getChildren();
        for(int a=0;a< qList.size();a++) {
            Element ques =(Element) qList.get(a);
            if(ques.getAttributeValue("file")!=null){
                //read xml
                System.out.println(ques.getAttributeValue("file"));
                //write xml attribute
                //System.out.println(ques.setAttribute("file","dasd"+a));
            }
            if(ques.getName().equalsIgnoreCase("question")){
                //read 
                System.out.println(ques.getTextTrim());
                ques.addContent(new CDATA(ques.getTextTrim()));
            }
            if (ques.getName().equalsIgnoreCase("options")) {
                List optList = ques.getChildren();
                for (int k = 0; k < optList.size(); k++) {
                    Element option = (Element) optList.get(k);
                    if(option.getName().equalsIgnoreCase("option")){
                        //read 
                        option.getParentElement().removeChild("option");
                    }
                }
            }
            if(ques.getName().equalsIgnoreCase("explaination")){
                ques.removeContent();
                ques.addContent(new CDATA("explaination"+a));
            }
        }
    }         
    FileOutputStream file=new FileOutputStream(path);
    xmlOutput.output(document, file);
}catch (JDOMException ex) {
    ex.printStackTrace();
} catch (IOException ex) {
    ex.printStackTrace();
}

my output is:

<?xml version="1.0" encoding ="utf-8" ?>
<mcss>
    <quest ans="1"> 
        <question><![CDATA[Write 5x= 3y-1 as linear equation form.]]></question>
        <options>

        </options>
        <explaination><![CDATA[Recall the linear equation in two variables form.]]></explaination>
    </quest>
</mcss>

but I want like this.

<?xml version="1.0" encoding ="utf-8" ?>
<mcss>
    <quest ans="1"> 
        <question><![CDATA[Write 5x= 3y-1 as linear equation form.]]></question>
        <options>
            <option><![CDATA[5x-3y+1=0]]></option>
            <option><![CDATA[-5x-3y-1=0]]></option>

        </options>
        <explaination><![CDATA[Recall the linear equation in two variables form.]]></explaination>
    </quest>
</mcss>

回答1:

Element.removeChild will remove only the first child with the given name. You can use Element.removeContent(int index) to remove child element by index

if (ques.getName().equalsIgnoreCase("options")) {
    ques.removeContent(2);
}

or Element.removeContent(Content content) to remove specific element.

if (ques.getName().equalsIgnoreCase("options")) {
    List<Element> options = ques.getChildren("option");
    if(options.size()>2) {
        Element optionToRemove = options.get(2);
        ques.removeContent(optionToRemove);
    }
}    

You said you want to remove the second option, but in your example third one is removed. I'm slightly confused, so change index if necessary.

回答2:

if (ques.getName().equalsIgnoreCase("options")) {
                         List optList = ques.getChildren();
                         for (int k = optList.size()-1; k < optList.size(); k++) {
                             Element option = (Element) optList.get(k);
                             if(option.getName().equalsIgnoreCase("option")){
                                //read 
                                option.getParentElement().removeChild("option");
                            }
                         }
                    }

just focus on the loop and iterate from last index -1 that i have done in code.