diff --git a/.idea/gradle.xml b/.idea/gradle.xml
index cb865f6..0897082 100644
--- a/.idea/gradle.xml
+++ b/.idea/gradle.xml
@@ -5,7 +5,7 @@
     <option name="linkedExternalProjectsSettings">
       <GradleProjectSettings>
         <option name="externalProjectPath" value="$PROJECT_DIR$" />
-        <option name="gradleJvm" value="jbr-17" />
+        <option name="gradleJvm" value="#GRADLE_LOCAL_JAVA_HOME" />
         <option name="modules">
           <set>
             <option value="$PROJECT_DIR$" />
diff --git a/app/src/main/java/com/example/oplogy/CreateUUID.java b/app/src/main/java/com/example/oplogy/CreateUUID.java
index 82924f1..e246aab 100644
--- a/app/src/main/java/com/example/oplogy/CreateUUID.java
+++ b/app/src/main/java/com/example/oplogy/CreateUUID.java
@@ -1,12 +1,26 @@
 package com.example.oplogy;
 
-import java.util.UUID;
+
+import java.util.List;
 
 public class CreateUUID {
 
-    public static String generateUUID() {
-        // UUIDを生成する処理
-        UUID uuid = UUID.randomUUID();
-        return uuid.toString();
+    public static String generateUUID(List<String> classIdList ){
+        while (true){
+            String uuid = String.valueOf((int)(Math.random()*100000));
+            boolean isDuplicate = false;
+            for(String classId : classIdList){
+                if(Integer.parseInt(classId) == Integer.parseInt(uuid)){
+                    //重複があればフラグを立て、ループを抜ける
+                    isDuplicate = true;
+                    break;
+                }
+            }
+            //重複がなければ生成したUUIDを返す
+            if (!isDuplicate) {
+                //firestoreに挿入処理
+                return uuid;
+            }
+        }
     }
 }
\ No newline at end of file
diff --git a/app/src/main/java/com/example/oplogy/FirestoreReception_classIdDatabase.java b/app/src/main/java/com/example/oplogy/FirestoreReception_classIdDatabase.java
new file mode 100644
index 0000000..258330a
--- /dev/null
+++ b/app/src/main/java/com/example/oplogy/FirestoreReception_classIdDatabase.java
@@ -0,0 +1,51 @@
+package com.example.oplogy;
+
+import android.util.Log;
+
+import com.google.android.gms.tasks.OnCompleteListener;
+import com.google.android.gms.tasks.Task;
+import com.google.firebase.firestore.CollectionReference;
+import com.google.firebase.firestore.DocumentSnapshot;
+import com.google.firebase.firestore.FirebaseFirestore;
+import com.google.firebase.firestore.QueryDocumentSnapshot;
+import com.google.firebase.firestore.QuerySnapshot;
+
+import org.checkerframework.checker.nullness.qual.NonNull;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+public class FirestoreReception_classIdDatabase {
+    private FirebaseFirestore db;
+    private List<String> classIdList= new ArrayList<>();
+
+    public FirestoreReception_classIdDatabase() {
+        db = FirebaseFirestore.getInstance();
+    }
+
+
+    public List<String> getAllDocumentsFromClassIdDatabase() {
+        db.collection("classId_Database")
+                .get()
+                .addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
+                    @Override
+                    public void onComplete(@NonNull Task<QuerySnapshot> task) {
+                        if (task.isSuccessful()) {
+                            for (QueryDocumentSnapshot document : task.getResult()) {
+                                Log.d("結果", document.getId() + " => " + document.getData());
+                                //データをListに追加
+                                classIdList.add((String) document.get("classId"));
+                            }
+                        } else {
+                            Log.d("結果", "Error getting documents: ", task.getException());
+                        }
+                    }
+                });
+
+        return classIdList;
+    }
+
+    public List<String> getClassIdList() {
+        return classIdList;
+    }
+}
\ No newline at end of file
diff --git a/app/src/main/java/com/example/oplogy/MainActivity.java b/app/src/main/java/com/example/oplogy/MainActivity.java
index 26ed954..5783546 100644
--- a/app/src/main/java/com/example/oplogy/MainActivity.java
+++ b/app/src/main/java/com/example/oplogy/MainActivity.java
@@ -45,6 +45,10 @@ public class MainActivity extends AppCompatActivity implements View.OnClickListe
     //firestoreの受信関連
     private FirebaseFirestore db;
     private FirestoreReception firestoreReception;
+    private FirestoreReception_classIdDatabase firestoreReception_classIdDatabase;
+
+    //取得するためのクラスID
+    private int classId=100000;
 
 
     @Override
@@ -80,7 +84,11 @@ public class MainActivity extends AppCompatActivity implements View.OnClickListe
         db = FirebaseFirestore.getInstance();
         firestoreReception = new FirestoreReception();
 
-        firestoreReception.getDocumentsByClassId(100);
+        //TODO:3.classIdをmainアクティビティで取得する手段を作る
+        //4.以上のことを実装するためにユーザーにid作成、setupをすることを促すような制限をかける
+        if(classId!=100000){
+            firestoreReception.getDocumentsByClassId(classId);
+        }
 
     }
 
@@ -137,15 +145,21 @@ public class MainActivity extends AppCompatActivity implements View.OnClickListe
     }
     //UUIDを表示するかのダイアログ
     private void showUUIDYesNoDialog() {
-        AlertDialog.Builder builder = new AlertDialog.Builder(this); // この 'this' が問題でないか確認
+        firestoreReception_classIdDatabase = new FirestoreReception_classIdDatabase();
+        List<String> classIdList = firestoreReception_classIdDatabase.getAllDocumentsFromClassIdDatabase();
+
+
+        AlertDialog.Builder builder = new AlertDialog.Builder(this);
         builder.setTitle("クラスID");
         builder.setMessage("あなたのクラスIDを表示しますか？");
 
         builder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
             @Override
             public void onClick(DialogInterface dialog, int which) {
-                String classId = CreateUUID.generateUUID();
+                String classId = CreateUUID.generateUUID(classIdList);
                 Toast.makeText(MainActivity.this, "クラスID: " + classId, Toast.LENGTH_SHORT).show();
+                Log .d("classIdList", classIdList.toString());
+
             }
         });
         builder.setNegativeButton("No", new DialogInterface.OnClickListener() {
@@ -227,8 +241,7 @@ public class MainActivity extends AppCompatActivity implements View.OnClickListe
                 .show();
     }
 
-
-    //Main
+    //提出状況の取得
     private ArrayList<SubmissionStudent> getSubmissionStudents() {
         ArrayList<SubmissionStudent> submissionStudents = new ArrayList<>();
         List<MyDataClass> myDataList = firestoreReception.getMyDataList();
diff --git a/app/src/main/java/com/example/oplogy/SetUpActivity.java b/app/src/main/java/com/example/oplogy/SetUpActivity.java
index 2dd4bdb..8b3385d 100644
--- a/app/src/main/java/com/example/oplogy/SetUpActivity.java
+++ b/app/src/main/java/com/example/oplogy/SetUpActivity.java
@@ -91,6 +91,7 @@ public class SetUpActivity extends FragmentActivity
             Intent intent = new Intent(SetUpActivity.this,MainActivity.class); //main画面へ戻る処理
             startActivity(intent);
         });
+        //TODO:.SetUpの際に、classIdを挿入すること
 
         setUp.setOnClickListener(view -> {
 
diff --git a/app/src/main/java/com/example/oplogy/SetUpTable.java b/app/src/main/java/com/example/oplogy/SetUpTable.java
index bc43841..a61ed27 100644
--- a/app/src/main/java/com/example/oplogy/SetUpTable.java
+++ b/app/src/main/java/com/example/oplogy/SetUpTable.java
@@ -16,6 +16,8 @@ public class SetUpTable {
     public String endBreakTime;
     public int totalStudent;
 
+    //TODO: ここのコードをあとで実装する。roomにString classIdの作成
+
 
     //コンストラクタ
     public SetUpTable(String teacherName, String startPoint, String startTime, String endTime,