Java 8, Lambda : replace Anonymous inner class by lambda

Question

I've got a class which contains the following:

List roles = ldapTemplate.search(baseDn, replaceFilter, sc,             new AttributesMapper() {                 public Object mapFromAttributes(Attributes attrs)                         throws NamingException {                     return attrs.get("cn").get();                 }             }); 

IntelliJ tells me to replace the anonymous inner class with a lambda. So I tried:

List roles = ldapTemplate.search(     baseDn, replaceFilter, sc,     (Attributes a)  -> { return a.get("cn").get(); }; ); 

However, I get a compilation error:

Error:(46, 50) java: incompatible types: inference variable T has incompatible bounds     equality constraints: java.lang.String     lower bounds: java.lang.Object 

I can't find the solution to this problem. Do you have any ideas?

Answer 1

Try this (removing extra semi colon)

List roles = ldapTemplate.search(     baseDn, replaceFilter, sc,     (Attributes a)  -> { return a.get("cn").get(); }             ); 

Answer 2

A simple azure storage Entity Resolver interface and it's implemented method:

EntityResolver<String> orderNumberResolver = new EntityResolver<String>() {     @Override     public String resolve(String partitionKey, String rowKey, Date timeStamp,         HashMap<String, EntityProperty> properties, String etag) {       return properties.get("SomeColumnName").getValueAsString();     }   }; 

Lambda of the above method will be :

 EntityResolver<String> orderNumberResolver = (           partitionKey, rowKey, timeStamp, properties, etag       ) -> properties.get("SomeColumnName").getValueAsString(); 

It's clear from above example that lambda's are smart enough to handle the type of method parameters according to their anonymous inner class thus it makes the implementation of overridden method easy. Hope this will be helpful.