How to Read Space-Separated Integers from a Text File in Java?

Read Space-Separated Integers from a Text File

In Java, reading data from a text file can be achieved using the Files class. This tutorial demonstrates how to read integers from a text file separated by spaces and store them in an ArrayList.

Step 1: Read the Text File

Use the readAllLines() method from the Files class to load the entire text file into a List with each line represented as a String.

Step 2: Split Each Line

Apply the split() method to each line to divide it into individual integers based on the whitespace character ("s "). This creates a List of String arrays.

Step 3: Convert Strings to Integers

To convert the String representations of integers into the actual type, use the valueOf() method of the Integer class.

Step 4: Add Integers to ArrayList

Using the add() method of the ArrayList, append each integer to the list.

Step 5: Assemble the ArrayList

Combining steps 1-4, here's a comprehensive code snippet:

List<Integer> numbers = new ArrayList<>();
for (String line : Files.readAllLines(Paths.get("/path/to/file.txt"))) {
    for (String part : line.split("\s+")) {
        Integer i = Integer.valueOf(part);
        numbers.add(i);
    }
}

Utilizing Java 8 Streams

In Java 8, the Stream API provides a more concise solution.

List<Integer> numbers = Files.lines(Paths.get("/path/to/file.txt"))
    .map(line -> line.split("\s+")).flatMap(Arrays::stream)
    .map(Integer::valueOf)
    .collect(Collectors.toList());

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