What's the right way to use iterators? 1

[cpjust]

Hi, I'm a C++ guy, and using iterators in C++ is simple.
Unfortunately, they work a lot differently in Java. :-(
In C++, I'd do something like this:

vector<string> strings;
...
for ( iterator<string> it = strings.begin(); it != strings.end(); ++it )
{
   cout << *it << endl;  // Print each string on a new line.
}

I tried doing this in Java:

Vector<String> strings;
...
iterator<String> it = Vector.iterator();
for ( String str = it.next(); it.hasNext(); str = it.next() )
{
   System.out.println( str );
}

But, it never prints the last index of the vector since the hasNext() returns false before the last string is pulled out of the iterator.

What's the Java equivalent of what I'd normally do in C++?

 

[stefanwagner]

Vector<String> strings;
...
for (String str : strings)
{
        System.out.println (str);
}

Read : as 'in'.
If you insist on an iterator:

		Vector <String> strings = new Vector <String> ();
		strings.add ("Foo");
		strings.add ("Bar");
		strings.add ("Foobar");
		
		Iterator <String> it = strings.iterator ();
		while (it.hasNext())
		{
			String str = it.next(); 
			System.out.println (str);
		}

Note: it is Iterator, not iterator, and strings.iterator (), not Vector.iterator.

Note: If you don't have a strong reason to use Vector, the usage of ArrayList is recommended.

		List <String> strings = new ArrayList <String> ();
		strings.add ("Foo");
		strings.add ("Bar");
		strings.add ("Foobar");
		for (String str : strings)
		{
		        System.out.println (str);
		}

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[cpjust]

Oops, I missed those typos.

Why is ArrayList better than a Vector?

If they're similar to their C++ counterparts, a vector is contiguous in memory like an array, and a list is a linked-list of elements.

A vector is usually preferred in C++ unless you plan on adding or deleting elements from the middle of the sequence.

 

[stefanwagner]

Vector contains code to make it synchronized, which affects its performance, whithout really reaching threadsafety.

For ArrayList you get indexed access like in Vector too.
Look at the javadocs for the public methods.
In the src.zip you may check the implementation.

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[cpjust]

OK thanks. I'll try that weird for (String str : strings) syntax...
I think I also saw something like that in a VBScript book (or maybe it was C#).