If file exists with same name then it will update the file with new version.

For register bean Class in service-context.xml file

<bean id="autoVersionByNameBehaviour" class="test.demoamp.AutoVersionByNameBehaviour" init-method="init">
     <property name="policyComponent" ref="policyComponent"/>
     <property name="nodeService" ref="NodeService"/>
     <property name="contentService" ref="ContentService"/>
     <property name="siteService" ref="SiteService" />
     <property name="fileFolderService" ref="FileFolderService"/>
     
     <property name="activityService" ref="activityService"/>
     </bean>

and the java class

import java.net.URLEncoder;

import org.alfresco.model.ContentModel;
import org.alfresco.repo.node.NodeServicePolicies;
import org.alfresco.repo.policy.Behaviour;
import org.alfresco.repo.policy.JavaBehaviour;
import org.alfresco.repo.policy.PolicyComponent;
import org.alfresco.service.cmr.activities.ActivityService;
import org.alfresco.service.cmr.model.FileFolderService;
import org.alfresco.service.cmr.model.FileInfo;
import org.alfresco.service.cmr.repository.ChildAssociationRef;
import org.alfresco.service.cmr.repository.ContentReader;
import org.alfresco.service.cmr.repository.ContentService;
import org.alfresco.service.cmr.repository.ContentWriter;
import org.alfresco.service.cmr.repository.NodeRef;
import org.alfresco.service.cmr.repository.NodeService;
import org.alfresco.service.cmr.site.SiteInfo;
import org.alfresco.service.cmr.site.SiteService;
import org.apache.commons.io.FilenameUtils;
import org.json.JSONStringer;
import org.json.JSONWriter;

public class AutoVersionByNameBehaviour
implements NodeServicePolicies.OnCreateNodePolicy {
    private PolicyComponent policyComponent;
    private NodeService nodeService;
    private ContentService contentService;
    private ActivityService activityService;
    private SiteService siteService;
    private FileFolderService fileFolderService;

    public void init() {
        this.policyComponent.bindClassBehaviour(NodeServicePolicies.OnCreateNodePolicy.QNAME, ContentModel.TYPE_CONTENT, (Behaviour)new JavaBehaviour((Object)this, "onCreateNode", Behaviour.NotificationFrequency.TRANSACTION_COMMIT));
    }

    public void onCreateNode(ChildAssociationRef childAssocRef) {
        NodeRef previouslyExistentDoc;
        NodeRef uploadedNodeRef = childAssocRef.getChildRef();
        if (this.nodeService.exists(uploadedNodeRef) && this.isContentDoc(uploadedNodeRef) && (previouslyExistentDoc = this.existedPreviousDocument(uploadedNodeRef)) != null) {
            ContentReader reader = this.contentService.getReader(uploadedNodeRef, ContentModel.PROP_CONTENT);
            ContentWriter writer = this.contentService.getWriter(previouslyExistentDoc, ContentModel.PROP_CONTENT, true);
            writer.putContent(reader);
            this.nodeService.addAspect(uploadedNodeRef, ContentModel.ASPECT_HIDDEN, null);
            this.postActivityUpdated(previouslyExistentDoc);
            this.nodeService.deleteNode(uploadedNodeRef);
        }
    }

    private void postActivityUpdated(NodeRef nodeRef) {
        SiteInfo siteInfo = this.siteService.getSite(nodeRef);
        String jsonActivityData = "";
        try {
            JSONWriter jsonWriter = new JSONStringer().object();
            jsonWriter.key("title").value((Object)this.nodeService.getProperty(nodeRef, ContentModel.PROP_NAME).toString());
            jsonWriter.key("nodeRef").value((Object)nodeRef.toString());
            StringBuilder sb = new StringBuilder("document-details?nodeRef=");
            sb.append(URLEncoder.encode(nodeRef.toString(), "UTF-8"));
            jsonWriter.key("page").value((Object)sb.toString());
            jsonActivityData = jsonWriter.endObject().toString();
        }
        catch (Exception e) {
            throw new RuntimeException(e);
        }
        FileInfo fileInfo = this.fileFolderService.getFileInfo(nodeRef);
        this.activityService.postActivity("org.alfresco.documentlibrary.file-updated", siteInfo == null ? null : siteInfo.getShortName(), siteInfo == null ? null : "documentLibrary", jsonActivityData, null, fileInfo);
    }

    private boolean isContentDoc(NodeRef nodeRef) {
        return this.nodeService.getType(this.nodeService.getPrimaryParent(nodeRef).getParentRef()).isMatch(ContentModel.TYPE_FOLDER);
    }

    private NodeRef existedPreviousDocument(NodeRef currentNodeRef) {
        String fileName = AutoVersionByNameBehaviour.cleanNumberedSuffixes(this.nodeService.getProperty(currentNodeRef, ContentModel.PROP_NAME).toString());
        if (!fileName.equals(this.nodeService.getProperty(currentNodeRef, ContentModel.PROP_NAME).toString())) {
            NodeRef folder = this.nodeService.getPrimaryParent(currentNodeRef).getParentRef();
            return this.nodeService.getChildByName(folder, ContentModel.ASSOC_CONTAINS, fileName);
        }
        return null;
    }

    public static String cleanNumberedSuffixes(String fileName) {
        String cleanedFileName = fileName;
        String baseName = FilenameUtils.getBaseName((String)fileName);
        if (baseName.indexOf("-") != -1 && AutoVersionByNameBehaviour.isInteger(baseName.substring(baseName.lastIndexOf("-") + 1, baseName.length()))) {
            return baseName.substring(0, baseName.lastIndexOf("-")) + FilenameUtils.EXTENSION_SEPARATOR_STR + FilenameUtils.getExtension((String)fileName);
        }
        return cleanedFileName;
    }

    public static boolean isInteger(String s) {
        boolean isValidInteger = false;
        try {
            Integer.parseInt(s);
            isValidInteger = true;
        }
        catch (NumberFormatException var2_2) {
            // empty catch block
        }
        return isValidInteger;
    }

    public void setPolicyComponent(PolicyComponent policyComponent) {
        this.policyComponent = policyComponent;
    }

    public void setNodeService(NodeService nodeService) {
        this.nodeService = nodeService;
    }

    public void setContentService(ContentService contentService) {
        this.contentService = contentService;
    }

    public void setActivityService(ActivityService activityService) {
        this.activityService = activityService;
    }

    public void setSiteService(SiteService siteService) {
        this.siteService = siteService;
    }

    public void setFileFolderService(FileFolderService fileFolderService) {
        this.fileFolderService = fileFolderService;
    }

}