Implement the Scanner

jlox/src/main/java/xyz/ctsk/lox/Lox.java

@@ -0,0 +1,62 @@
+package xyz.ctsk.lox;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.nio.charset.Charset;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+
+public class Lox {
+    private static boolean hadError = false;
+     private static void run(String source) {
+        var scanner = new Scanner(source);
+        scanner.scanTokens().forEach(System.out::println);
+    }
+
+    static void error(int line, String message) {
+         report(line, "", message);
+    }
+
+    private static void report(int line, String where, String message) {
+         System.err.printf("[line %d] Error %s: %s%n", line, where, message);
+         hadError = true;
+    }
+
+
+    private static void runPrompt() throws IOException {
+        var input = new InputStreamReader(System.in);
+        var reader = new BufferedReader(input);
+
+        while (true) {
+            System.out.println("> ");
+            String line = reader.readLine();
+            if (line == null) break;
+            run(line);
+            hadError = false;
+        }
+    };
+
+    private static void runFile(String path) throws IOException {
+        byte[] bytes = Files.readAllBytes(Paths.get(path));
+        run(new String(bytes, Charset.defaultCharset()));
+
+        if (hadError) {
+            System.exit(65);
+        }
+    }
+
+    private static void printUsage() {
+        System.out.println("Usage: jlox [script]");
+    }
+
+    public static void main(String[] args) throws IOException {
+        if (args.length == 0) {
+            runPrompt();
+        } else if (args.length == 1) {
+            runFile(args[0]);
+        } else {
+            printUsage();
+        }
+    }
+}