Convert array of strings into a string in Java

Concrete join methods

StringBuilder: For custom scenarios

Need a mutable sequence of characters or have unusual requirements? StringBuilder is your buddy:

String[] words = {"Java", "is", "mighty"};
StringBuilder sb = new StringBuilder();
for (String word : words) {
    sb.append(word).append(" ");  // Adding SpaceStation after each word
}
sb.setLength(sb.length() - 1); // Shhh...Last trailing space didn't pay rent!
String result = sb.toString();
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When in Android land, use TextUtils.join()

For Android developers, TextUtils.join() acts as a lifesaver:

String[] words = {"Android", "coding", "is", "fun"};
String result = TextUtils.join(" ", words); 
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Third-party libraries: There's an Apache for that

Got Apache Commons Lang or Guava's Joiner handy? They've got you covered:

// Wind of Apache blowing your way
String[] words = {"Java", "enhances", "creativity"};
String result = StringUtils.join(words, " ");

// Going nuts with Guava's Joiner
String[] words = {"Practically", "Java", "rocks"};
String result = Joiner.on(" ").skipNulls().join(words);
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Considerations and trapdoors

This sign says "No += allowed in loops"

Incrementing += for concatenation in a loop? Not so fast! It ends up creating excess string objects:

String res = "";
for(String word : words) {
    res += word + " "; // Don't do that. It's traumatizing for Java!
}
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Big arrays? Beware of memory footprint

Handling gargantuan arrays? Keep an eye on memory usage:

// Pray to the JVM gods for memory!
String[] bigArray = createAMassiveArrayOfStrings();
String result = String.join(" ", bigArray);
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Going the extra mile

Null handling with finesse

Have an array that might contain null? Choose the right method:

String[] words = {"Java", null, "is", null, "versatile"};
String result = Arrays.stream(words)
    .filter(Objects::nonNull)
    .collect(Collectors.joining(" "));
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Multithreading needs StringBuffer

Calling StringBuffer to the rescue in multithreaded scenarios:

StringBuffer sb = new StringBuffer();
// Thread-safe operations happening here!
String result = sb.toString();
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No explicit arrays needed with pipeline

Forge a path directly within a stream pipeline:

String result = Stream.of("Pro", "Java", "Tips")
    .collect(Collectors.joining(", "));
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