Java8 map Object property to another property in List Stream - dictionary

Question

I need to map the 'count' property of the Source objects Stream to Target object's regCount & otherCount properties based on the indicator field by grouping them with PoNum property [ Ex : if (indicator.equals("Y") ? regCount = 15: otherCount = 400)]
Currently I'm doing something like the below
Map<Integer, List<SourceBean>> srcMap = srcBeanList.stream()
.collect(Collectors.groupingBy(SourceBean::getPoNum, Collectors.toList()));
for (Entry<Integer, List<SourceBean>> entry : srcMap.entrySet()) {
TargetBean tgtBean = new TargetBean();
for(SourceBean srcBean : entry.getValue()) {
tgtBean.setPoNum(srcBean.getPoNum());
tgtBean.setVendor(srcBean.getVendor());
if(srcBean.getIndicator().equals("N")) {
tgtBean.setRegCount(srcBean.getLblCnt());
}
else if(srcBean.getIndicator().equals("Y")) {
tgtBean.setOtherCount(srcBean.getLblCnt());
}
}
tgtBeanBeanList.add(tgtBean);
}
Please suggest how to achieve this mapping in Java 8 stream mapping possibly using flatmap
public class SourceBean {
private Integer poNum;
private String vendor;
private String indicator (Y/N);
private Integer count;
}
Source Json
[
{
"poNum" : 2490,
"count" : 15,
"vendor" : "Vend A",
"indicator " : "Y"
}, {
"poNum" : 2490,
"count" : 400,
"vendor" : "Vend A",
"indicator " : "N"
}
]
public class TargetBean {
private Integer poNum;
private String vendor;
private String regCount;
private String otherCount;
}
Target Json
[
{
"poNum" : 2490,
"regCount" : 15,
"otherCount" : 400,
"vendor" : "Vend A"}
]

Answer 1

I define a transform method named List2Bean(): it help to realize your forloop logic about combine SourceBeanList into one TargetBean. However it returns a List to apply for stream operation.
And then, focus on how I use .values().stream().map() operation. It is the key to realize your logic.
public class Test {
public TargetBean List2Bean(List<SourceBean> sourceBeanList){
TargetBean tgtBean = new TargetBean();
for(SourceBean srcBean : sourceBeanList) {
tgtBean.setPoNum(srcBean.getPoNum());
tgtBean.setVendor(srcBean.getVendor());
if(srcBean.getIndicator().equals("N")) {
tgtBean.setRegCount(String.valueOf(srcBean.getCount()));
}
else if(srcBean.getIndicator().equals("Y")) {
tgtBean.setOtherCount(String.valueOf(srcBean.getCount()));
}
}
return tgtBean;
}
public static void main(String[] args){
Test test = new Test();
List<SourceBean> srcBeanList = new ArrayList<>();
srcBeanList.add(new SourceBean(2490, "Vend A", "Y", 15));
srcBeanList.add(new SourceBean(2490, "Vend A", "N", 400));
Map<Integer, List<SourceBean>> srcMap = srcBeanList.stream()
.collect(Collectors.groupingBy(SourceBean::getPoNum, Collectors.toList()));
//List<TargetBean> targetBeanList = (List<TargetBean>)
List<TargetBean> tgtMaplist =
srcMap.values().stream().map( e -> {return test.List2Bean(e.getValue());})
.collect(Collectors.toList());
tgtMaplist.stream().forEach(t -> {
System.out.println(t.getPoNum() + " " + t.getVendor() + " " + t.getRegCount() + " " + t.getOtherCount() );
});
}
}