How to convert a List<String> into a comma separated string without iterating List explicitly

Full suite of methods

Sure, Java 8's String.join() is a convenient tool for turning your list into a single string, but like any good developer's toolkit, we've got more gadgets at our disposal.

Using StringUtils

Ah, Apache Commons Lang, the friendly neighbourhood helper library.

// commons-lang3 in action - magically turning lists into strings since 2001
String result = StringUtils.join(list, ", ");
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Bingo! Just make sure this friendly helper is part of your gang (included in your project dependencies).

Board the Guava train

Google's Guava library sprints to our rescue with its Joiner.

// Joining the "Guava" gang. Who said Google only knows Search and Gmail? 
String result = Joiner.on(", ").join(list);
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Joiner dazzles as it handles those tricky nulls without breaking a sweat, and can even be customized to your liking.

toString() - Pushing the boundaries

Here's a sly little trick, a bit of toying with toString().

// WARNING: Mad scientist in action! Proceed with caution 
String result = list.toString().replaceAll("(^\\[|\\]$)", "").replace(", ", ",");
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This might give you a wild ride, especially if your List<String> elements are carrying commas themselves - expect the unexpected!

Know your battleground

Each of these warriors have their unique traits. Choose wisely:

• Null elements: String.join() might bite you when it encounters null, while Apache and Guava might be more forgiving.
• Commas in strings: When your List<String> elements smuggle in commas, things can get messy if you're not careful.
• Performance: The big guys - Apache Commons Lang and Guava - often come with neat tweaks for speedier manipulations. String.join() has its own share of magic for regular and smaller lists.

Match the method to your madness

Perfect method to tame your List<String> beast:

• Vanilla Java: String.join(), no frills, no complications.
• Special treatment for nulls: StringUtils.join or Guava's Joiner, they're your men.
• Custom crafting: With list.toString() you can be the sculptor. But remember, with complexity, comes great responsibility.

Benefits of skipping iteration

Skipping explicit loops while converting lists to strings also makes you skip heartbeats:

• Readability matters: Cleaner code, clearer thought process.
• Boilerplate be gone: Say goodbye to verbose loop structures.
• Error-proofing: Why bother with loop logic when the method can do it for you.

Problem-specific scenarios

Let's look at some code examples tailored to specific scenarios and requirements.

Simple and single-use scenarios:

// "I'm walking on sunshine, woah!"
String result = String.join(", ", list);
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Straightforward and simple.

Handling null explicitly:

// "You shall not pass!" - Gandalf the Null. 
String result = list.stream()
    .filter(Objects::nonNull)
    .collect(Collectors.joining(", "));
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Stay alert for the null invaders.

Preparing for serialization:

// No extra spaces allowed in this strict school!
String result = String.join(",", list); 
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Spick and span for serialization.