# WS-07 – Multithreading Basics and Hashing

---

## Mini Student Search Engine

### Goal

Create a simple student search engine that:

1. Reads students from a file
2. Processes data using multiple threads
3. Stores students inside lists
4. Supports search by ID
5. Overrides `hashCode()` and `equals()`

---

## Project Structure

```
WS-07-Multithreading-Basics-and-Hashing/
│
├── students.txt
│
├── src/main/java/dev/
│   │
│   ├── Main.java
│   │
│   ├── model/
│   │   └── Student.java
│   │
│   ├── thread/
│   │   └── StudentLoader.java
│   │
│   ├── service/
│   │   └── StudentManager.java
│   │
│   └── utils/
│       └── FileManager.java
│
└── README.md
```

---

## Input File

`students.txt`

```txt
1001,Ali,Computer Science,3.7
1002,Sara,Physics,3.9
1003,John,Mathematics,3.5
1004,Alice,Chemistry,3.2
1005,David,Computer Science,3.8
```

Format:

```txt
id,name,major,gpa
```

---

## Part 1 – Student Class

Create:

```java
Student
```

Fields:

```java
int id;
String name;
String major;
double gpa;
```

Override:

```java
hashCode()

equals(Object obj)

toString()
```

Rules:

Students are equal if IDs are equal.

Example:

```java
Student s1 = new Student(1001,...);
Student s2 = new Student(1001,...);

s1.equals(s2); // true
```

Custom hash:

```java
return id % 97;
```

Do NOT use:

```java
Objects.hash()
```

---

## Part 2 – Student Loader Thread

Create:

```java
StudentLoader extends Thread
```

Each thread receives part of file lines.

Example:

Thread 1:

```txt
1001
1002
```

Thread 2:

```txt
1003
1004
```

Thread 3:

```txt
1005
```

Each thread:

1. Reads assigned lines
2. Creates Student objects
3. Stores them in its own list

Example:

```java
Thread1 → listA

Thread2 → listB

Thread3 → listC
```

No shared list.

Do NOT use:

```java
synchronized
Lock
Semaphore
ExecutorService
```

---

# Part 3 – Merge Results

After threads finish:

```java
thread1.join();
thread2.join();
thread3.join();
```

Combine results:

```java
finalList.addAll(listA);

finalList.addAll(listB);

finalList.addAll(listC);
```

---

## Required Menu

```txt
1.Load students
2.Search student
3.Remove student
4.Print students
5.Exit
```

Search example:

```txt
ID:1002

Found:

Student{id=1002,name=Sara}
```

---

## Restrictions

Forbidden:

```java
HashMap
HashSet
TreeMap
ConcurrentHashMap

synchronized
wait()
notify()

Lock
Semaphore

ExecutorService
```

Allowed:

```java
Thread
join()

ArrayList

FileReader
BufferedReader
```