Actually lambda expressions aren't "just an abbreviation to implement anonymous classes". The benefit of using lambda expression is that it has direct access to instance of this class (the class from which it was called), while anonymous class don't (it has its own this instance).
In other words, anonymous classes introduce a new scope. so that names are resolved from their superclasses and interfaces and can shadow names that occur in the lexically enclosing environment. For lambdas, all names are resolved lexically.
https://stackoverflow.com/a/22640484 And also
Lambda performance with Anonymous classes
When application is launched each class file must be loaded and verified.
Anonymous classes are processed by compiler as a new subtype for the given class or interface, so there will be generated a new class file for each.
Lambdas are different at bytecode generation, they are more efficient, used invokedynamic instruction that comes with JDK7.
For Lambdas this instruction is used to delay translate lambda expression in bytecode untill runtime. (instruction will be invoked for the first time only)
As result Lambda expression will becomes a static method(created at runtime). (There is a small difference with stateles and statefull cases, they are resolved via generated method arguments)
https://stackoverflow.com/a/33874965
For instance:
interface Supplier {
void foo();
}
class A {
private String name;
public void doSome() {
baz(() -> System.out.println(this.name));
}
private void baz(Supplier sup){
sup.foo();
}
}
or
class A {
private String name;
public void doSome() {
baz(new Supplier() {
void foo() {
System.out.println(A.this.name);
}
});
}
private void baz(Supplier sup){
sup.foo();
}
}
I recommend to read this: Java8 Lambdas vs Anonymous classes.
Answer from Andrew Kolesnyk on Stack OverflowActually lambda expressions aren't "just an abbreviation to implement anonymous classes". The benefit of using lambda expression is that it has direct access to instance of this class (the class from which it was called), while anonymous class don't (it has its own this instance).
In other words, anonymous classes introduce a new scope. so that names are resolved from their superclasses and interfaces and can shadow names that occur in the lexically enclosing environment. For lambdas, all names are resolved lexically.
https://stackoverflow.com/a/22640484 And also
Lambda performance with Anonymous classes
When application is launched each class file must be loaded and verified.
Anonymous classes are processed by compiler as a new subtype for the given class or interface, so there will be generated a new class file for each.
Lambdas are different at bytecode generation, they are more efficient, used invokedynamic instruction that comes with JDK7.
For Lambdas this instruction is used to delay translate lambda expression in bytecode untill runtime. (instruction will be invoked for the first time only)
As result Lambda expression will becomes a static method(created at runtime). (There is a small difference with stateles and statefull cases, they are resolved via generated method arguments)
https://stackoverflow.com/a/33874965
For instance:
interface Supplier {
void foo();
}
class A {
private String name;
public void doSome() {
baz(() -> System.out.println(this.name));
}
private void baz(Supplier sup){
sup.foo();
}
}
or
class A {
private String name;
public void doSome() {
baz(new Supplier() {
void foo() {
System.out.println(A.this.name);
}
});
}
private void baz(Supplier sup){
sup.foo();
}
}
I recommend to read this: Java8 Lambdas vs Anonymous classes.
The x is not recognized as a field from the Age interface. You have to either do a static import (import static Age.x) or specify where the x comes from:
Age oj1 = () -> System.out.print("Age is "+ Age.x);
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.
Try this (removing extra semi colon)
List roles = ldapTemplate.search(
baseDn, replaceFilter, sc,
(Attributes a) -> { return a.get("cn").get(); }
);
An anonymous inner class (AIC) can be used to create a subclass of an abstract class or a concrete class. An AIC can also provide a concrete implementation of an interface, including the addition of state (fields). An instance of an AIC can be referred to using this in its method bodies, so further methods can be called on it, its state can be mutated over time, etc. None of these apply to lambdas.
I'd guess that the majority of uses of AICs were to provide stateless implementations of single functions and so can be replaced with lambda expressions, but there are other uses of AICs for which lambdas cannot be used. AICs are here to stay.
UPDATE
Another difference between AICs and lambda expressions is that AICs introduce a new scope. That is, names are resolved from the AIC's superclasses and interfaces and can shadow names that occur in the lexically enclosing environment. For lambdas, all names are resolved lexically.
Lambdas though a great feature, will only work with SAM types. That is, interfaces with only a single abstract method. It would fail as soon as your interface contains more than 1 abstract method. That is where anonymous classes will be useful.
So, no we cannot just ignore anonymous classes. And just FYI, your sort() method can be more simplified, by skipping the type declaration for p1 and p2:
Collections.sort(personList, (p1, p2) -> p1.firstName.compareTo(p2.firstName));
You can also use method reference here. Either you add a compareByFirstName() method in Person class, and use:
Collections.sort(personList, Person::compareByFirstName);
or, add a getter for firstName, directly get the Comparator from Comparator.comparing() method:
Collections.sort(personList, Comparator.comparing(Person::getFirstName));
