LESSON 374 OF 410 · PROJECTS: COMMAND-LINE TOOLS

CLI Tool: head v2 — First n Lines in Java

Practice

Extend your head command to take an integer n and return the first n lines of lines, joined by newline characters (\n). For this version you may assume 0 ≤ n ≤ lines.size(). If n is 0 the result is the empty string.

Function signature:

public String head(List<String> lines, int n)

Example:

Input: lines = ["alpha", "beta", "gamma", "delta", "epsilon"], n = 3

Output: "alpha\nbeta\ngamma"

When printed:
alpha
beta
gamma

Use List.subList(0, n) for the first n elements, then String.join("\n", ...). Since the problem guarantees n ≤ lines.size(), no min needed.

Combine the two calls into one:

return String.join("\n", lines.subList(0, n));

The full solution:

class Solution {
    public String head(List<String> lines, int n) {
        return String.join("\n", lines.subList(0, n));
    }
}

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CLI Tool: head v2 — First n Lines in Java

Head V2 in Java