How to set repeated fields in protobuf before building the message?

Question

Let's say I have a Message with a repeated field:

Message Foo {
    repeated Bar bar = 1;
}

Now I want to insert n Bar objects into the field bar, each is created in a loop.

for (i=0; i < n; i++){
    //Add Bar into foo
}
//Build foo after loop

Is this possible or do I need all n bar fields at the same time before building the foo Object?

Answer 1

When you use the protoc command to generate the java object it will create a Foo Object which will have its own builder method on it.

You will end up doing something like this

//Creates the builder object 
Builder builder = Package.Foo.newBuilder();
//populate the repeated field.
builder.addAll(new ArrayList<Bar>());
//This should build out a Foo object
builder.build(); 

To add individual objects you can do something like this.

    Bar bar = new Bar();
    builder.addBar(bar);
    builder.build();

Edited with the use case you've requested.

Answer 2

List<Bar> barList= new Arraylist();
barList.add(new Bar());

Then set the list of Bar in the Foo

Foo foo =  Foo.newBuilder()
        .addAllBar(barList)
        .build;

You can set only one value for Bar

Foo foo =  Foo.newBuilder()
        .addBar(new Bar())
        .build;