Initial

.envrc

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+use flake .

.gitignore

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+# Compiled class file
+*.class
+
+# Log file
+*.log
+
+# BlueJ files
+*.ctxt
+
+# Mobile Tools for Java (J2ME)
+.mtj.tmp/
+
+# Package Files #
+*.jar
+*.war
+*.nar
+*.ear
+*.zip
+*.tar.gz
+*.rar
+
+# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
+hs_err_pid*
+replay_pid*

Action.java

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+public class Action {
+  private String name;
+  private int damage;
+
+  public Action() {}
+  
+  public Action(String name, int damage) {
+    this.name = name;
+    this.damage = damage;
+  }
+
+  public int getDamage() {
+    return damage;
+  }
+
+  public String getName() {
+    return name;
+  }
+
+  public void setDamage(int damage) {
+    this.damage = damage;
+  }
+
+  public void setName(String name) {
+    this.name = name;
+  }
+}

ActionHistory.java

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+public class ActionHistory {
+    private class Node<T> {
+        private T content = null;
+        private Node nextNode = null;
+
+        public Node(T content) {
+          setContent(content);
+        }
+
+        private void setContent(T content) {
+            this.content = content;
+        }
+
+        private T getContent() {
+            return this.content;
+        }
+
+        private void setNextNode(Node nextNode) {
+            this.nextNode = nextNode;
+        }
+
+        private Node getNextNode() {
+            return this.nextNode;
+        }
+    }
+
+    private Node head = null;
+
+    public ActionHistory() {}
+
+    public boolean isEmpty() {
+      if (head == null) {
+        return true;
+      }
+      return false;
+    }
+
+    public void push(Object content) {
+      if (isEmpty()) {
+         head = new Node(content);
+      } else {
+        Node newNode = new Node(content);
+        newNode.setNextNode(head);
+        head = newNode;
+      }
+    }
+
+    public Object pop() {
+      if (isEmpty()) {
+        return null;
+      }
+      Object content = head.getContent();
+      head = head.getNextNode();
+      return content;
+    }
+
+    public Object top() {
+      return ((isEmpty()) ? null : head.getContent());
+    }
+}

GNUmakefile

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+JAVA_FMT   = google-java-format
+JAVA_FILES = $(shell find . -name '*.java')
+XML_FMT = xmlindent
+XML_FILES = $(shell find . -name '*.xml')
+
+.PHONY: fmt
+fmt:
+	@echo "Formatting all Java files..."
+	@for f in $(JAVA_FILES); do \
+		echo "  $$f"; \
+		$(JAVA_FMT) -i $$f; \
+	done

Main.java

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+public class Main {
+    public static void main(String[] args) {
+        Action delete = new Action("delete", 12);
+        Action changeFont = new Action("changeFont", 0);
+        Action bold  = new Action("bold", 1);
+
+        ActionHistory actionHistory = new ActionHistory();
+        System.out.println(actionHistory.isEmpty());
+        actionHistory.push(delete);
+        actionHistory.push(changeFont);
+        System.out.println("+ 2 Items pushed");
+        
+        System.out.println(actionHistory.isEmpty());
+        System.out.println(actionHistory.pop());
+        System.out.println(actionHistory.pop());
+        System.out.println("- 2 Items poped");
+        actionHistory.pop();
+        
+        actionHistory.push(bold);
+        System.out.println("+ 1 Item pushed");
+        
+        System.out.println(actionHistory.isEmpty());
+        System.out.println("Action top: " + actionHistory.top());
+        System.out.println(actionHistory.pop());
+        System.out.println("- 1 Item poped");
+        System.out.println(actionHistory.isEmpty());
+        System.out.println("Action top: " + actionHistory.top());
+    }
+}

flake.nix

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+{
+  description = "Stack";
+
+  inputs = {
+    flake-parts.url = "github:hercules-ci/flake-parts";
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+  };
+
+  outputs = inputs@{ flake-parts, ... }:
+    flake-parts.lib.mkFlake { inherit inputs; } {
+      imports = [ ];
+      systems =
+        [ "x86_64-linux" "aarch64-linux" "aarch64-darwin" "x86_64-darwin" ];
+      perSystem = { config, self', inputs', pkgs, system, ... }:
+        let
+
+          jdk = pkgs.jdk21.override { };
+
+          buildInputs = [ jdk ];
+
+          devTools = [ pkgs.google-java-format ];
+
+        in {
+          devShells.default =
+            pkgs.mkShell { buildInputs = buildInputs ++ devTools; };
+
+          packages = {
+            default = pkgs.stdenv.mkDerivation {
+              pname = "stack";
+              version = "1.0.0";
+
+              src = ./.;
+
+              nativeBuildInputs = buildInputs ++ [ pkgs.makeWrapper ];
+
+              buildPhase = ''
+                javac -Werror -g:none -deprecation -verbose Main.java
+              '';
+
+              installPhase = ''
+                mkdir -p $out/{bin,lib}
+                cp *.class $out/lib
+
+                makeWrapper ${
+                  pkgs.lib.getExe jdk
+                } $out/bin/stack --add-flags "-cp $out/lib/ Main"
+              '';
+            };
+          };
+        };
+      flake = { };
+    };
+}