Comparable和Comparator的区别

Posted 2020-08-28

Comparable

Comparable是由需要比较的类自己实现(implements)此接口，并实现其中的compareTo方法，之后对象可直接使用Collection.sort方法进行排序等

public class OrgNode implements Comparable {
    private Logger log = LoggerFactory.getLogger(OrgNode.class);

    private long orgId;
    private String name;
    private long sortId;

    private List<OrgNode> children = new ArrayList<OrgNode>();

    public OrgNode(long orgId, String name) {
        this.orgId = orgId;
　　　　　this.name = name;
    }

    public List<OrgNode> getChildren() {
        if (children == null) {
            children = new ArrayList<OrgNode>();
        }

        Collections.sort(children);

        return Collections.unmodifiableList(children);
    }
  
    @Override
    public int compareTo(Object obj) {
        OrgNode orgNodeTmp = (OrgNode) obj;
        return new Long(this.sortId).compareTo(orgNodeTmp.sortId);
    }
　　public long getOrgId() {
    　　return orgId;
　　}

　　public String getName() {
    　　return name;
　　}

　　public long getSortId() { return sortId; } 

　　public void setSortId(long sortId) { this.sortId = sortId; }
}

 

Comparator

Comparator是在需要比较类的外面自定义的一个比较器，并实现compare方法。在使用Collection.sort时，把实现的比较器当作第二个参数传入：

public class OrgNodeComparator implements Comparator<OrgNode> {

    @Override
    public int compare(OrgNode o1, OrgNode o2) {
        return new Long(o1.getSortId()).compareTo(o2.getSortId());
    }
    
}

public class OrgNode {
    private Logger log = LoggerFactory.getLogger(OrgNode.class);

    private long orgId;
    private String name;
    private long sortId;

    private List<OrgNode> children = new ArrayList<OrgNode>();

    public OrgNode(long orgId, String name) {
        this.orgId = orgId;
　　　　　this.name = name;
    }

    public List<OrgNode> getChildren() {
        if (children == null) {
            children = new ArrayList<OrgNode>();
        }

        Collections.sort(children, new OrgNodeComparator());
　　  　 return Collections.unmodifiableList(children);
    } 

 　　public long getOrgId() { 　　return orgId; 　　}
 　　public String getName() { 　　return name; 　　}
 　　public long getSortId() { return sortId; }
 　　public void setSortId(long sortId) { this.sortId = sortId; }
 }