Internal vs. External Iterators

Java supports both external and internal iteration styles.

External Iteration

The caller pulls elements:

• explicit Iterator
• enhanced for
• manual traversal control

This style is strong when the caller needs fine control over stopping, branching, or state.

Internal Iteration

The collection or pipeline drives traversal:

• streams
• callbacks
• higher-order operations

This style is strong when the operation can be expressed declaratively.

Review Rule

Choose the iteration style that makes control flow clearest. If the caller needs to own traversal decisions, external iteration is often better.