Question

I have seen it first time ... in a method signature.

I tried to access a .class file. It has a method defined as below

public void addGraphData(GraphData... _graphData) {
}

And that GraphData is nothing but POJO with getters and setters. Why is the .class file displaying GraphData... _graphData instead of GraphData _graphData ??

Answer 1

It’s varargs and can only be used last in a parameter list. The last param can hold more than one object.

public class C { 

    int i;
    String[] s;

    public C(int i, String... s){
        this.i = i;
        this.s=s;
    }
}
new C(4,"a","b") // will be transformed to int and String[]

See how “a” and “b” has transformed into an array.