49) SERIALIZATION

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Mon Jul 08 2024 13:19:26 GMT+0000 (Coordinated Universal Time)

Saved by @varuntej #java

Serialization program with 3 files

import java.io.*;

public class Student implements Serializable
{
	private int id;
	private String name;
	private double percentage;
	
	// use transient and static variables to check if they are saved
	
	public Student(int id, String name, double percentage)
	{
		this.id = id;
		this.name = name;
		this.percentage = percentage;
	}
	
	public String toString()
	{
		return "ID: "+this.id+", Name: "+this.name+", Percentage: "+this.percentage;
	}
}





import java.io.*;

public class SerializationDemo
{
	public static void main(String[] args)
	{
		try(FileOutputStream fos = new FileOutputStream("serial.txt");
		    ObjectOutputStream out = new ObjectOutputStream(fos);
		   )
		   {   System.out.println("Creating a student");
			   Student s = new Student(100, "John", 98.56);
			   System.out.println(s);
			   out.writeObject(s);
			   System.out.println("Object serialized");
		   }
		   catch(FileNotFoundException fe){ fe.printStackTrace();}
		   catch(IOException ie){ ie.printStackTrace(); }
	}
}

import java.io.*;

public class DeserializationDemo
{
	public static void main(String[] args)
	{
		try(FileInputStream fis = new FileInputStream("serial.txt");
		    ObjectInputStream in = new ObjectInputStream(fis);
		   )
		   {   System.out.println("Restoring the object");
			   Student s = (Student)in.readObject();
			   System.out.println(s);
			   System.out.println("Deserialization Done");
		   }
		   catch(ClassNotFoundException ce){ ce.printStackTrace();}
		   catch(IOException ie){ ie.printStackTrace(); }
	}
}

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OOP'S JAVA

@varuntej

1)OPERATORS TASK 1A 2)Student grade task 1B 3)command line arguments 1C 4)Constructor and method overloading task 2a 5)type casting task 2B 6)Use array sum of integers and find the sum and average of the elements of that array in java 7)Practice further programs on the usage of arrays in java 8)Write a program to utilize both standard and custom packages. The program should reflect the usage of packages in a correct manner, along with the purpose of access modifiers 9))Write a program to use gc() method of both System and Runtime classes. Experiment with other methods of those classes. 10)write a program using the hierarchy of employees in a university 11))Write a program to understand polymorphic invocation of methods,while overriding the methods. Use an employee base class and manager sub class; override the computeSalary() method to illustrate the concept. 12)Develop an application that uses inheritance. Use the class Account and then subclass it into different account types. Then making use of Customer and Employee classes to develop the application to reflect the nature of banking operations. Use minimum operational sequence. 13)Demonstrate the use of abstract classes. Write a Person abstract class and then subclass that into Student and Faculty classes. Use appropriate fields and methods. 14)Write a program to demonstrate the usage of interfaces. 15)Write a program to understand the full capability of String class.Implement as many methods as required. Consult API documentation to read through the methods. 16)Write programs using StringBuffer and StringBuilder library classes. 17)Write a program to demonstrate the usage of try and associated keywords. Introduce bugs into the program to raise exceptions and then catch and process them. 18)Learn how to create and use custom exceptions. 19)Using byte streams, write a program to both read from and write to files. 20)Using FileReader and FileWriter, write a program to perform file copying and any other suitable operations. 21)Write a Java Program that displays the number of characters, lines and words in a text file. 22)Use the classes StringTokenizer, StringReader and StringWriter to write a program to find the capabilities of these classes. 23)Write a program to demonstrate enumerations and usage of Assertions. 24) Demonstrate assertions through simple programs. 25)Write programs to illustrate the use of Thread class and Runnable interface. 26)Write a program to show the assignment of thread priorities. 27)Write a program to synchronize threads. Use Producer and Consumer problem to illustrate the concept. 28) LABEL DEMO 29) BUTTON DEMO 30) CHECK BOX DEMO 31) RADIO BUTTON DEMO 32) COMBO BOX DEMO 1 33) COMBO BOX DEMO 2 34) LIST DEMO 35) TEXT DEMO 36) File input stream demo(IO) 37) file output stream demo(IO) 38) file input stream demo (BYTE) 39) file OUTput stream demo (BYTE) 40) BUFFERED INPUT STREAM DEMO (BYTE) 41) BUFFERED OUTPUT STREAM DEMO (BYTE) 42)Byte Array Output sTream Demo (BYTE) 43) Byte Array Input Stream Demo (BYTE) 44) FILE READER & WRITER DEMO (CHAR) 45) Char Array Reader & WRITER Demo (CHAR) 46) CHAR BUFFER READER & WRITER DEMO (CHAR) 47) FILE FUNCTIONS (IO) 48) DIR LIST & CONSOLE DEMO 49) SERIALIZATION 50) INTER THREAD COMMUNICATION

#java #howto #interviewquestions #mobile

How to use Java Swing to create a button

import javax.swing.*;  
public class FirstSwingExample {  
public static void main(String[] args) {  
JFrame f=new JFrame();//creating instance of JFrame  
          
JButton b=new JButton("click");//creating instance of JButton  
b.setBounds(130,100,100, 40);//x axis, y axis, width, height  
          
f.add(b);//adding button in JFrame  
          
f.setSize(400,500);//400 width and 500 height  
f.setLayout(null);//using no layout managers  
f.setVisible(true);//making the frame visible  
}  
}

#java #gfg #geeksforgeeks #lecture #recursion #rope cutting

Rope Cutting Problem

import java.io.*;
import java.util.*;

class GFG 
{
	static int maxCuts(int n, int a, int b, int c)
	{
		if(n == 0) return 0;
		if(n < 0)  return -1;

		int res = Math.max(maxCuts(n-a, a, b, c), 
		          Math.max(maxCuts(n-b, a, b, c), 
		          maxCuts(n-c, a, b, c)));

		if(res == -1)
			return -1;

		return res + 1; 
	}
  
    public static void main(String [] args) 
    {
    	int n = 5, a = 2, b = 1, c = 5;
    	
    	System.out.println(maxCuts(n, a, b, c));
    }
}

#java #interviewquestions #search

How to binary search in Java

import java.util.Stack;

/**
 * Java Program to implement a binary search tree. A binary search tree is a
 * sorted binary tree, where value of a node is greater than or equal to its
 * left the child and less than or equal to its right child.
 * 
 * @author WINDOWS 8
 *
 */
public class BST {

    private static class Node {
        private int data;
        private Node left, right;

        public Node(int value) {
            data = value;
            left = right = null;
        }
    }

    private Node root;

    public BST() {
        root = null;
    }

    public Node getRoot() {
        return root;
    }

    /**
     * Java function to check if binary tree is empty or not
     * Time Complexity of this solution is constant O(1) for
     * best, average and worst case. 
     * 
     * @return true if binary search tree is empty
     */
    public boolean isEmpty() {
        return null == root;
    }

    
    /**
     * Java function to return number of nodes in this binary search tree.
     * Time complexity of this method is O(n)
     * @return size of this binary search tree
     */
    public int size() {
        Node current = root;
        int size = 0;
        Stack<Node> stack = new Stack<Node>();
        while (!stack.isEmpty() || current != null) {
            if (current != null) {
                stack.push(current);
                current = current.left;
            } else {
                size++;
                current = stack.pop();
                current = current.right;
            }
        }
        return size;
    }


    /**
     * Java function to clear the binary search tree.
     * Time complexity of this method is O(1)
     */
    public void clear() {
        root = null;
    }

}

#java #java #arraylists #while-loops #equala

How to insert ArrayList into While-condition?

List<String> songList = new ArrayList<>();
songList.add("Some song"); //Repeat until satisfied

System.out.println("\n\tWelcome! Please choose a song!");
String songChoice = scan.nextLine();
while (!songList.contains(songChoice)) {
    //Do stuff when input is not a recognised song
}

#java #gfg #geeksforgeeks #arrays #practice #frequencycount #frequencies #limitedrange

Frequencies of Limited Range Array Elements

class Solution{
    //Function to count the frequency of all elements from 1 to N in the array.
    public static void frequencyCount(int arr[], int N, int P)
    {
        //Decreasing all elements by 1 so that the elements
        //become in range from 0 to n-1.
        int maxi = Math.max(P,N);
        int count[] = new int[maxi+1];
        Arrays.fill(count, 0);
        for(int i=0;i<N;i++){
            count[arr[i]]++; 
        }
        
        for(int i=0;i<N;i++){
            arr[i] = count[i+1];
        }
    }
}

How to efficiently iterate over each entry in a Java Map

Map<String, String> map = ...
for (Map.Entry<String, String> entry : map.entrySet()) {
    System.out.println(entry.getKey() + "/" + entry.getValue());
}

Print Nested Array in Java

String[][] deepArray = new String[][] {{"John", "Mary"}, {"Alice", "Bob"}};
System.out.println(Arrays.toString(deepArray));
//output: [[Ljava.lang.String;@106d69c, [Ljava.lang.String;@52e922]
System.out.println(Arrays.deepToString(deepArray));

#java #java #2dchar array

How do you check a row in a 2D char array for a specific element and then count how many of that element are in the row? (Java)

private boolean oneQueenPerRow() {
    int foundQueens;
    for (int i = 0; i < board.length; i++) {
        foundQueens = 0;//each loop is a checked row
        for (int j = 0; j < board.length; j++) {
            if (board[i][j] == QUEEN)
                foundQueens++;
        }
        if (foundQueens > 1) return false;
    }
    return true;
}

#java #logic #algorithms #interesting #arrays

Flood Fill Algorithm: Like the bucket tool in Paint app but for multi-dimensional arrays

import java.util.ArrayDeque;
import java.util.Arrays;
import java.util.Queue;

class Pair {
    int x, y;

    public Pair(int x, int y) {
        this.x = x;
        this.y = y;
    }
}

class FloodFill
{
    // Below arrays details all 8 possible movements
    private static final int[] row = { -1, -1, -1, 0, 0, 1, 1, 1 };
    private static final int[] col = { -1, 0, 1, -1, 1, -1, 0, 1 };

    // check if it is possible to go to pixel (x, y) from
    // current pixel. The function returns false if the pixel
    // has different color or it is not a valid pixel
    public static boolean isSafe(char[][] M, int m, int n,
                                int x, int y, char target)
    {
        return x >= 0 && x < m && y >= 0 && y < n
                && M[x][y] == target;
    }

    // Flood fill using BFS
    public static void floodfill(char[][] M, int x, int y, char replacement)
    {
        int m = M.length;
        int n = M[0].length;

        // create a queue and enqueue starting pixel
        Queue<Pair> q = new ArrayDeque<>();
        q.add(new Pair(x, y));

        // get target color
        char target = M[x][y];

        // run till queue is not empty
        while (!q.isEmpty())
        {
            // pop front node from queue and process it
            Pair node = q.poll();

            // (x, y) represents current pixel
            x = node.x;
            y = node.y;

            // replace current pixel color with that of replacement
            M[x][y] = replacement;

            // process all 8 adjacent pixels of current pixel and
            // enqueue each valid pixel
            for (int k = 0; k < row.length; k++)
            {
                // if adjacent pixel at position (x + row[k], y + col[k]) is
                // a valid pixel and have same color as that of current pixel
                if (isSafe(M, m, n, x + row[k], y + col[k], target))
                {
                    // enqueue adjacent pixel
                    q.add(new Pair(x + row[k], y + col[k]));
                }
            }
        }
    }

    public static void main(String[] args)
    {
        // matrix showing portion of the screen having different colors
        char[][] M = {
            "YYYGGGGGGG".toCharArray(),
            "YYYYYYGXXX".toCharArray(),
            "GGGGGGGXXX".toCharArray(),
            "WWWWWGGGGX".toCharArray(),
            "WRRRRRGXXX".toCharArray(),
            "WWWRRGGXXX".toCharArray(),
            "WBWRRRRRRX".toCharArray(),
            "WBBBBRRXXX".toCharArray(),
            "WBBXBBBBXX".toCharArray(),
            "WBBXXXXXXX".toCharArray()
        };

        // start node
        int x = 3, y = 9;   // target color = "X"

        // replacement color
        char replacement = 'C';

        // replace target color with replacement color
        floodfill(M, x, y, replacement);

        // print the colors after replacement
        for (int i = 0; i < M.length; i++) {
            System.out.println(Arrays.toString(M[i]));
        }
    }
}

Finding all classes implementing a specific interface

public <T> List<Class<? extends T>> findAllMatchingTypes(Class<T> toFind) {
    foundClasses = new ArrayList<Class<?>>();
    List<Class<? extends T>> returnedClasses = new ArrayList<Class<? extends T>>();
    this.toFind = toFind;
    walkClassPath();
    for (Class<?> clazz : foundClasses) {
        returnedClasses.add((Class<? extends T>) clazz);
    }
    return returnedClasses;
}

#java #gfg #geeksforgeeks #lecture #sorting #bubblesort

// Optimised Bubble Sort

import java.io.*;

class GFG {
    
    static void bubbleSort(int arr[], int n){
        boolean swapped;
        
        for(int i = 0; i < n; i++){
            
            swapped = false;
            
            for(int j = 0; j < n - i - 1; j++){
                if( arr[j] > arr[j + 1]){
                    
                    // swapping
                    int temp = arr[j];
                    arr[j] = arr[j+1];
                    arr[j+1] = temp;
                    
                    swapped = true;
                    
                }
            }
            if(swapped == false)
            break;
        }
    }
    
	public static void main (String[] args) {
	    int a[] = {2, 1, 4, 3};
	    bubbleSort(a, 4);
	    
	    for(int i = 0; i < 4; i++){
	        System.out.print(a[i] + " ");     // OUTPUT : 1 2 3 4
	    }
	}
}






// Bubble Sort

import java.io.*;

class GFG {
    
    static void bubbleSort(int arr[], int n){
        for(int i = 0; i < n; i++){
            for(int j = 0; j < n - i - 1; j++){
                if( arr[j] > arr[j + 1]){
                    
                    // swapping
                    int temp = arr[j];
                    arr[j] = arr[j+1];
                    arr[j+1] = temp;
                    
                }
            }
        }
    }
    
	public static void main (String[] args) {
	    int a[] = {2, 1, 4, 3};
	    bubbleSort(a, 4);
	    
	    for(int i = 0; i < 4; i++){
	        System.out.print(a[i] + " ");     // OUTPUT : 1 2 3 4
	    }
	}
}

#java #gfg #geeksforgeeks #lecture #sorting #selectionsort

import java.io.*;

class GFG {
    
    static void selectionSort(int arr[], int n){
        for(int i = 0; i < n; i++){
            int min_ind = i;
            
            for(int j = i + 1; j < n; j++){
                if(arr[j] < arr[min_ind]){
                    min_ind = j;
                }
            }
            
            int temp = arr[i];
            arr[i] = arr[min_ind];
            arr[min_ind] = temp;
        }
    }
    
	public static void main (String[] args) {
	    int a[] = {2, 1, 4, 3};
	    selectionSort(a, 4);
	    
	    for(int i = 0; i < 4; i++){
	        System.out.print(a[i] + " ");    // OUTPUT : 1 2 3 4
	    }
	}
}

Intent to Start New Activity in Android Studio

// IntendedActivity - the file you wish to open
// CurrentActivity - the file where this code is placed  

Intent intent = new Intent (this, IntendedActivity.class);
    CurrentActivity.this.startActivity(intent);

Insertion Sort in Java

 public void sort(int array[]) { 
     for (int i = 1; i < array.length; i++) { 
          int key = array[i]; 
          int j = i - 1; 
          while (j >= 0 && array[j] > key) { 
              array[j + 1] = array[j]; 
              j = j - 1; 
          } 
          array[j + 1] = key; 
      } 
 }

> More steps

Storing data in SQLite Database in android

public class LocalDatabase extends SQLiteOpenHelper {
         
    private static final String mDatabaseName = "LocalDatabase";
    private static final int mDatabaseVersion = 1;

public LocalDatabase(Context context) {
        super(context, mDatabaseName, null, mDatabaseVersion);
        SQLiteDatabase db = this.getWritableDatabase();
    }      

}

> More steps

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