Most Used Java Stream Map Functions

Retriving a List of attribute (field) values from a Object List (Array List)

List users=new ArrayList<>();
List userIds=users
            .stream()
            .map(u->u.getId())
            .collect(Collectors.toList());

Filter Objects by Attribute in a Array List

        
List users=new ArrayList<>();
List filteredUsers=users
            .stream()
            .filter(u->u.getId().equals(1l))
            .collect(Collectors.toList());

Check if All Values of a Array List Matches a Cirtain Condition

checking if all the users in the list are having active status

        
List users=new ArrayList<>();
if(users.stream().allMatch(u->u.getStatus().equalsIgnoreCase("active"))){
   //checking if all the users in the list are having active status
}

Check if atleast one Value of a Array List Matches a Cirtain Condition

checking if atleast one user in the list has active status

        
List users=new ArrayList<>();
if(users.stream().anyMatch(u->u.getStatus().equalsIgnoreCase("active"))){
   //checking if atleast one user in the list has active status
}

Check if None of the Values of a Array List Matches a Cirtain Condition

checking none of the users in the list are having active status

        
List users=new ArrayList<>();
if(users.stream().noneMatch(u->u.getStatus().equalsIgnoreCase("active"))){
   //checking none of the users in the list are having active status
}

Filter Object Array List by Condition and Count Results

 
List users=new ArrayList<>();
Long count=users
            .stream()
            .filter(u->u.getStatus().equalsIgnoreCase("active"))
            .count();

Find the Firts matched result from Array List As a Optional Value

 
List users=new ArrayList<>();
Optional optionalUser=users
            .stream()
            .filter(u->u.getEmail().equalsIgnoreCase("abc@techbootstrap.com"))
            .findFirst();

optionalUser.ifPresent(u->{
    //user presents with above condition,
    //do something with the value
});