I would like to know how do I convert the following lambda expression to a for-each loop:
private static List<GrantedAuthority> mapToGrantedAuthorities(List<Authority> authorities) {
return authorities.stream()
.map(authority -> new SimpleGrantedAuthority(authority.getName().name()))
.collect(Collectors.toList());
}
That should work:
List<GrantedAuthority> list = new ArrayList<GrantedAuthority>();
for(Authority auth : authorities)
list.add(new SimpleGrantedAuthority(auth.getName().name()));
return list;
I guess you are using java lower than 1.8, that's why you want to do that, it's probably faster too.
You could also use Google Guava (https://github.com/google/guava) to get somewhat closer to the Java 8 style in previous Java versions:
private static List<GrantedAuthority> mapToGrantedAuthorities(final List<Authority> authorities) {
return Lists.transform(authorities, new Function<Authority,GrantedAuthority>(){
@Override
public GrantedAuthority apply(Authority authority) {
return new SimpleGrantedAuthority(authority.getName().name());
}
});
}
The basis of Lambda Expressions is that the Lambda takes a class with one method only, in this case it is doing a foreach loop with the stream, and is creating a new SimpleGrantedAuthority using the name from the list being passed in and then returning another list of authorities.
So it is taking a list of Authorities and returning the same List but as GrantedAuthorities.
List<GrantedAuthority> granted = new ArrayList<GrantedAuthority>();
for( Authority auth : authorities)
{
granted.add(new SimpleGrantedAuthority(auth.getName().name()));
}
return granted;
