How does the append method differ from the concatenation operation when working with StringBuilder in Java?

In Java, StringBuilder is used for efficient string construction without creating new objects on each modification. The append method adds data to the current content of the StringBuilder and modifies its internal buffer.

Concatenation operation (+) when working with strings creates new String objects, which is less efficient, especially in loops or with multiple modifications.

When it comes to concatenation using StringBuilder, it is usually also a call to the append method. The difference is that append modifies the existing object, whereas string concatenation with + creates new objects.

Example:

StringBuilder sb = new StringBuilder();
sb.append("Hello");
sb.append(" World");
System.out.println(sb.toString()); // Hello World

Using append is preferable for multiple additions, as it saves memory and improves performance compared to string concatenation with +.