Using java stream to replace the complex code

Question

I have the below code block which I'm trying to convert using java stream.

for(Emp emp:empList){
            if(combinedData.getOrg()==null){
                combinedData.setOrg(emp.getCompany());
            }
            combinedData.addToList(emp.getWorkLog());
            if(combinedData.getRawData()!=null){
                combinedData.setRawData(combinedData.getRawData()+emp.getData());
            }
            else{
                combinedData.setRawData(emp.getData());
            }
        }

The challenge I have is that I need to set Org only one and also I need to append to the existing rawdata. I know it can be easily done with reduced number of lines using streams.

The complete code is below

public class Main {
    public static void main(String[] args) {
        List<Emp> empList = Arrays.asList(
                new Emp("x1","as2112","a"),
                new Emp("x1","as2122","b"),
                new Emp("x1","as2422","c"),
                new Emp("x1","as2423","d"));
        CombinedData combinedData = new CombinedData();
        for(Emp emp:empList){
            if(combinedData.getOrg()==null){
                combinedData.setOrg(emp.getCompany());
            }
            combinedData.addToList(emp.getWorkLog());
            if(combinedData.getRawData()!=null){
                combinedData.setRawData(combinedData.getRawData()+emp.getData());
            }
            else{
                combinedData.setRawData(emp.getData());
            }
        }

}

}
class Emp{
    private String company;
    private String workLog;
    private String data;

    public Emp(
            String company,
            String workLog,
            String data) {
        this.company = company;
        this.workLog = workLog;
        this.data = data;
    }

    public String getCompany() {
        return company;
    }

    public void setCompany(String company) {
        this.company = company;
    }

    public String getWorkLog() {
        return workLog;
    }

    public void setWorkLog(String workLog) {
        this.workLog = workLog;
    }

    public String getData() {
        return data;
    }

    public void setData(String data) {
        this.data = data;
    }
}

class CombinedData{
    private String org;
    private List<String> worklogList;
    private String rawData;

    public String getOrg() {
        return org;
    }

    public void setOrg(String org) {
        this.org = org;
    }

    public List<String> getWorklogList() {
        return worklogList;
    }

    public void setWorklogList(List<String> worklogList) {
        this.worklogList = worklogList;
    }

    public String getRawData() {
        return rawData;
    }

    public void setRawData(String rawData) {
        this.rawData = rawData;
    }
    public void addToList(String worklog){
        this.worklogList.add(worklog);
    }
}

Your code causes a NullPointerException (CombinedData.addToList())! — Samuel Philipp
– Samuel Philipp, Commented Apr 22, 2019 at 18:28

Alexander Pavlov · Accepted Answer · 2019-04-22 18:26:50Z

2

I know it can be easily done with reduced number of lines using streams.

Well, it is not true. I only can advise you to add method to CombinedData

void add(Emp emp) {
    if(getOrg()==null){
        setOrg(emp.getCompany());
    }
    addToList(emp.getWorkLog());
    if(getRawData()!=null){
        setRawData(getRawData()+emp.getData());
    }
    else{
        setRawData(emp.getData());
    }
}

and then apply it to the stream

CombinedData combinedData = new CombinedData();
empList.forEach(combinedData::add);

answered Apr 22, 2019 at 18:26

Alexander Pavlov

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Comments

Thomas Bitonti · Accepted Answer · 2019-04-22 18:37:52Z

0

As an aside, this particular step is better as an operation of 'combinedData':

if ( combinedData.getRawData() != null ) {
    combinedData.setRawData( combinedData.getRawData() + emp.getData() );
} else{
    combinedData.setRawData( emp.getData() );
}

combinedData.addRawData( emp.getData() );

What is telling is that the code has several calls to 'combinedData'. Does the caller really need to know the state of 'combinedData', or how to combine existing raw data with new raw data (implemented here by concatenation)?

(Also, placing the step in this fashion works much much better if ever you were to add synchronization / had to make this code thread safe.)

answered Apr 22, 2019 at 18:37

Thomas Bitonti

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