CODEWITHSUNDEEP
javacollectionslambdahashmapjava-8
user35443
user35443

Reputation: 6403

Java 8: HashMap initialization with lambda expressions

I'm trying to declare and define larger hash map at once. This is how I do it:

public HashMap<Integer, Callable<String>> opcode_only = new HashMap<Integer, Callable<String>>() {{
    put(x, y);
    put(x, y);
}};

But, when I try to use lambda expressions in body of put, I'm hitting on eclipse warrning/error. This is how I use lambda in HashMap:

public HashMap<Integer, Callable<String>> opcode_only = new HashMap<Integer, Callable<String>>() {{
    put(0, () -> { return "nop"; });
    put(1, () -> { return "nothing...."; });
}};

Eclipse underlines whole part of lambda starting with comma before. Error messages:

Syntax error on token ",", Name expected    
Syntax error on tokens, Expression expected instead

Does anybody know what am I doing wrong? Is initialization by lambda expression allowed in HashMap? Please help.

Upvotes: 15

Views: 21432

Answers (3)

Nitin Mahesh
Nitin Mahesh

Reputation: 3842

You are doing correct, update JDK library to 1.8 version from Java Build Path in Eclipse Project properties.

I just now tried the below code and it is working fine on my Eclipse:

        HashMap<Integer, Integer> hmLambda = new HashMap<Integer, Integer>() {
        {
            put(0, 1);
            put(1, 1);
        }
    };
    System.out.println(hmLambda.get(0));

    hmLambda.forEach((k, v) -> System.out.println("Key " + k
            + " and Values is: " + v));

Upvotes: 4

flumingo
flumingo

Reputation: 513

As far as I know Netbeans 7.4 fully supports Java 8. I had Problems with eclipse (atm it's not supporting java8 so it's just able to compile the old Lambda expressions of 7), that's why i switched to Netbeans. If you've installed an earlier Version of Netbeans please make sure to FULLY uninstall it to make sure the newer one isn't able to refer to old Logfiles etc.

Upvotes: 0

MohamedSanaulla
MohamedSanaulla

Reputation: 6242

This works fine in the Netbeans Lamba builds downloaded from: http://bertram2.netbeans.org:8080/job/jdk8lambda/lastSuccessfulBuild/artifact/nbbuild/

import java.util.*;
import java.util.concurrent.Callable;

public class StackoverFlowQuery {

  public static void main(String[] args) throws Exception {

    HashMap<Integer, Callable<String>> opcode_only = 
          new HashMap<Integer, Callable<String>>() {
            {
              put(0, () -> {
                return "nop";
              });
              put(1, () -> {
                return "nothing....";
              });
            }
          };
    System.out.println(opcode_only.get(0).call());
  }

}

Upvotes: 7

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