From fc066c315113652ba6831b4dbb74aeacc55b39cb Mon Sep 17 00:00:00 2001
From: TienNM99 <tiennm99@outlook.com>
Date: Wed, 27 Sep 2023 23:19:35 +0700
Subject: [PATCH] [Init]

---
 .gitignore    |  3 +++
 src/Main.java | 35 +++++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 src/Main.java

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..f63a24e
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,3 @@
+.idea
+*.iml
+out
diff --git a/src/Main.java b/src/Main.java
new file mode 100644
index 0000000..cbd59a9
--- /dev/null
+++ b/src/Main.java
@@ -0,0 +1,35 @@
+import java.io.BufferedWriter;
+import java.io.FileWriter;
+import java.io.IOException;
+
+public class Main {
+
+  public static void main(String[] args) {
+    int n = 1_000_000_000; // Upper limit
+    boolean[] isPrime = new boolean[n + 1];
+
+    for (int i = 2; i <= n; i++) {
+      isPrime[i] = true;
+    }
+
+    for (int p = 2; p * p <= n; p++) {
+      if (isPrime[p]) {
+        for (int i = p * p; i <= n; i += p) {
+          isPrime[i] = false;
+        }
+      }
+    }
+
+    try (BufferedWriter writer = new BufferedWriter(new FileWriter("primes.txt"))) {
+      for (int i = 2; i <= n; i++) {
+        if (isPrime[i]) {
+          writer.write(Integer.toString(i));
+          writer.newLine();
+        }
+      }
+      System.out.println("Prime numbers up to " + n + " have been saved to primes.txt.");
+    } catch (IOException e) {
+      e.printStackTrace();
+    }
+  }
+}