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Wednesday, 13 May 2015

Transforming Java Collections with Guava's Collections2

We can transform java objects using guava .
import java.util.ArrayList;
import java.util.List;

import com.google.common.base.Function;
import com.google.common.collect.Lists;

public class TransformExample {

    public static void main(String[] args) {

        ArrayList<User> users = new ArrayList<User>();
        users.add(new User("java", 10));
        users.add(new User("c", 30));
        users.add(new User("php", 40));
        users.add(new User("html", 100));
        users.add(new User("javascript", 500));
        users.add(new User("css", 300));

        Function<User, Long> userIdsConvert = new Function<User, Long>() {
            public Long apply(User user) {
                return user.getUserId();
            }
        };
        List<Long> userIds = Lists.transform(users, userIdsConvert);

        for (Long id : userIds) {
            System.out.println("userId is=" + id);
        }

    }
}

class User {
    private String name;
    private long userId;

    public User(String name, long userId) {
        super();
        this.name = name;
        this.userId = userId;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public long getUserId() {
        return userId;
    }

    public void setUserId(long userId) {
        this.userId = userId;
    }

}



Output:

userId is=10
userId is=30
userId is=40
userId is=100
userId is=500
userId is=300



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