Lesson 4.4: Store and Process a List

A list stores several related values in a specific order. Each position has an index, which is a number used to find one item.

The Blockly list menu calls the first position item 1. Java uses index 0 for the first item, so a Java array with three items has valid indexes 0, 1, and 2. The data stays in the same order even though the displayed position starts differently.

Store a list in a variable when several parts of the program need it. A loop can process each item instead of using a separate command for every position.

Lists can contain numbers, text, or Boolean values. Keeping related items the same type usually makes later operations clearer.

Guided practice

Create the list [4, 7, 2] and store it in scores. Print item 1, then item 3. Predict both outputs.

Use a for each item in list loop to print every score. Count how many times the loop body runs. Then add each item to a variable named total and print the final total after the loop.

Java arrays and lists use the same main ideas: ordered items, indexes, length, and repeated processing.

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