ArrayList对象的运行时输入被视为字符串

Question

I'm trying to add Objects to ArrayList, during static inputs, it's working fine

class ArrayListDemo4
{
    public static void main(String[] args) 
    {
        Collection cl = new ArrayList();
        cl.add(true);cl.add("Hello");cl.add(6.55f);cl.add(566);
        out.println(cl);

        for(Object o: cl)
            System.out.println(o.getClass());
    }
}

Output:

D:\COLLECTIONS>java ArrayListDemo4
[true, Hello, 6.55, 566]
class java.lang.Boolean
class java.lang.String
class java.lang.Float
class java.lang.Integer

When I'm trying to do the same with runtime inputs, the getClass() is giving only as String. I noticed that next() has 2 signatures with different return types public java.lang.String next(), public java.lang.Object next() and generalized console input to Object

class ArrayListDemo3 
{
    public static void main(String[] args) 
    {
        Scanner  input = new Scanner(in);
        List cl = new ArrayList(4);

        out.println("Enter the objects to the ArrayList:");
        for (int i =0; i < 4; i++ )
        {out.print("cl["+i+"]   =  ");  cl.add((Object)input.next());   }
        out.println(cl);

        for(Object o: cl)
        {out.println(o.getClass());}
    }
}

Output:

Enter the objects to the ArrayList:
cl[0]   =  true
cl[1]   =  Hello
cl[2]   =  6.55f
cl[3]   =  566
[true, Hello, 6.55f, 566]
class java.lang.String
class java.lang.String
class java.lang.String
class java.lang.String

Can someone please correct/help me with - how do I get respective Object types for runtime entered values?

Answer 1

Consult with java.util.Scanner javadoc, and you will find that next() always returns String .

At the same time java.util.Scanner has lots of methods to get values of specific types: nextBoolean() , nextByte() , etc.

Also, I would strongly suggest: do not use collections of raw types . Java has pretty good generics mechanism. So, if you are in the process of learning - here is good resource to start.