Java codeimport java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
public class StudyMap {
public static void main(String[] args) {
HashMap> result = new HashMap>();
List testList = new ArrayList();
testList.add(new OKBean(1, 0));
testList.add(new OKBean(2, 0));
testList.add(new OKBean(3, 0));
testList.add(new OKBean(4, 1));
testList.add(new OKBean(5, 1));
testList.add(new OKBean(6, 1));
testList.add(new OKBean(7, 2));
testList.add(new OKBean(8, 2));
testList.add(new OKBean(9, 2));
testList.add(new OKBean(10, 4));
testList.add(new OKBean(11, 4));
testList.add(new OKBean(12, 4));
for (OKBean okbean : testList) {
List okbeans = result.get(okbean.getParentId());
if (okbeans == null) {
okbeans = new ArrayList();
result.put(okbean.getParentId(), okbeans);
}
okbeans.add(okbean);
}
displayMap(result, 1, "");
}
public static void displayMap(HashMap> result,
int startKey, String str) {
List list = result.get(startKey);
for (OKBean okBean : list) {
System.out.println(str + okBean.getId() + ":");
if (result.containsKey(okBean.getId())) {
displayMap(result, okBean.getId(), str + " ");
}
}
}
}
class OKBean {
public OKBean() {
}
public OKBean(int id, int parentId) {
this.id = id;
this.parentId = parentId;
}
private int id;
private int parentId;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public int getParentId() {
return parentId;
}
public void setParentId(int parentId) {
this.parentId = parentId;
}
}
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