{"id":1353,"date":"2021-05-23T05:46:17","date_gmt":"2021-05-23T05:46:17","guid":{"rendered":"https:\/\/codeinsightacademy.com\/blog\/?p=1353"},"modified":"2021-05-25T14:10:00","modified_gmt":"2021-05-25T14:10:00","slug":"java-cheat-sheet","status":"publish","type":"post","link":"https:\/\/codeinsightacademy.com\/blog\/java\/java-cheat-sheet\/","title":{"rendered":"Java Cheat Sheet"},"content":{"rendered":"\n

Softwares to Install
<\/p>\n\n\n\n

JDK 11
https:\/\/www.oracle.com\/in\/java\/technologies\/javase-jdk11-downloads.html<\/a><\/p>\n\n\n\n

Apache Tomcat Server (version 9)
https:\/\/tomcat.apache.org\/download-90.cgi<\/a><\/p>\n\n\n\n

Eclipse EE (2021)
https:\/\/www.eclipse.org\/downloads\/packages\/release\/neon\/3\/eclipse-ide-java-ee-developers<\/a><\/p>\n\n\n\n

Xampp for MySQL (latest version)
https:\/\/www.apachefriends.org\/download.html<\/a><\/p>\n\n\n\n

Postman for REST API
https:\/\/www.postman.com\/downloads\/<\/a><\/p>\n\n\n\n

Addition of Two Numbers<\/strong><\/p>\n\n\n\n

class Main {\n\t\n\tpublic static void main(String args[]) {\n\t\tSystem.out.println(args[0]);\n\t\tSystem.out.println(args[1]);\n\t\t\n\t\tint num1 = Integer.parseInt(args[0]);\n\t\tint num2 = Integer.parseInt(args[1]);\n\n\t\tint add = num1 + num2;\n\t\t\n\t\tSystem.out.println(String.format(\"%s + %s = %s\", num1, num2, add));\n\t}\n\t\n}<\/code><\/pre>\n\n\n\n
Inheritance<\/strong><\/p>\n\n\n\n
class Bank {\n\t\n\tprotected int balance;\n\t\n\tpublic Bank(int bal) {\n\t\tthis.balance = bal;\n\t\tSystem.out.println(String.format(\"Account opened with Balance: %s\", this.balance));\n\t}\n\t\n\tpublic void deposit(int amt) {\n\t\tSystem.out.println(String.format(\"Deposit Amount: %s\", amt));\n\t\tthis.balance += amt;\n\t}\n\t\n\tpublic void withdraw(int amt) {\n\t\tSystem.out.println(String.format(\"Withdraw Amount: %s\", amt));\n\t\tthis.balance -= amt;\n\t}\n\t\n\tpublic void showBalance() {\n\t\tSystem.out.println(String.format(\"Available Balance: %s\", this.balance));\n\t}\n\t\n}\n\nclass HDFC extends Bank {\n\tpublic HDFC(int bal) {\n\t\tsuper(bal);\n\t}\n}\n\nclass SBI extends Bank {\n\tpublic SBI(int bal) {\n\t\tsuper(bal);\n\t}\n\t\n\tpublic void withdraw(int amt) {\n\t\tsuper.withdraw(amt);\n\t\tsuper.balance -= 20;\n\t}\n\t\n}\n\nclass Main {\n\tpublic static void main(String args[]) {\n\t\tBank bobj = new Bank(1000);\n\t\tbobj.showBalance();\n\t\tbobj.deposit(500);\n\t\tbobj.showBalance();\n\t\tbobj.withdraw(300);\n\t\tbobj.showBalance();\n\t\t\n\t\tSystem.out.println(\"====================\");\n\t\t\n\t\tHDFC hobj = new HDFC(2000);\n\t\thobj.showBalance();\n\t\thobj.deposit(500);\n\t\thobj.showBalance();\n\t\thobj.withdraw(300);\n\t\thobj.showBalance();\n\t\t\n\t\tSystem.out.println(\"====================\");\n\t\t\n\t\tSBI sobj = new SBI(3000);\n\t\tsobj.showBalance();\n\t\tsobj.deposit(500);\n\t\tsobj.showBalance();\n\t\tsobj.withdraw(300);\n\t\tsobj.showBalance();\n\t}\n}\n<\/code><\/pre>\n\n\n\n
Exception Handling<\/strong><\/p>\n\n\n\n
class Main {\n\tpublic static void main(String args[]) {\n\t\ttry {\n\t\t\t\n\t\t\tint num1 = Integer.parseInt(args[0]);\n\t\t\tint num2 = Integer.parseInt(args[1]);\n\t\t\t\n\t\t\ttry {\n\t\t\t\tint div = num1 \/ num2;\n\t\t\t\tSystem.out.println(String.format(\"Division of %s and %s is %s\", num1, num2, div));\n\t\t\t} catch (Exception e) {\n\t\t\t\tSystem.out.println(e);\n\t\t\t}\n\t\t\t\n\t\t\t\n\t\t} catch (ArrayIndexOutOfBoundsException aie) {\n\t\t\tSystem.out.println(aie);\n\t\t\t\n\t\t} catch (Exception e) {\n\t\t\tSystem.out.println(e);\n\t\t}\n\t\t\n\t}\n}<\/code><\/pre>\n\n\n\n
Servlet Demo<\/strong><\/p>\n\n\n\n
Servlet Life Cycle<\/p>\n\n\n\n
\"\"\/<\/figure>\n\n\n\n
  1. form.html<\/li><\/ol>\n\n\n\n
    <!DOCTYPE html>\n<html>\n<head>\n<meta charset=\"ISO-8859-1\">\n<title>Addition of 2 numbers<\/title>\n<link\n\thref=\"https:\/\/cdn.jsdelivr.net\/npm\/bootstrap@5.0.1\/dist\/css\/bootstrap.min.css\"\n\trel=\"stylesheet\"\n\tintegrity=\"sha384-+0n0xVW2eSR5OomGNYDnhzAbDsOXxcvSN1TPprVMTNDbiYZCxYbOOl7+AMvyTG2x\"\n\tcrossorigin=\"anonymous\">\n<\/head>\n<body class=\"container\">\n\t<form action=\"CalcServlet\" class=\"m-5\">\n\t\t<div class=\"row\">\n\t\t\t<div class=\"col\">Number 1<\/div>\n\t\t\t<div class=\"col\">\n\t\t\t\t<input type=\"text\" name=\"num1\" placeholder=\"Enter number\" autofocus>\n\t\t\t<\/div>\n\t\t<\/div>\n\t\t<div class=\"row\">\n\t\t\t<div class=\"col\">Number 1<\/div>\n\t\t\t<div class=\"col\">\n\t\t\t\t<input type=\"text\" name=\"num2\" placeholder=\"Enter number\">\n\t\t\t<\/div>\n\t\t<\/div>\n\t\t<div class=\"row\">\n\t\t\t<div class=\"col\">\n\t\t\t\t<input class=\"btn btn-primary\" type=\"submit\" value=\"Calculate\" \/>\n\t\t\t<\/div>\n\t\t<\/div>\n\t<\/form>\n<\/body>\n<\/html><\/code><\/pre>\n\n\n\n
    2. CalcServlet<\/p>\n\n\n\n
    import java.io.IOException;\nimport java.io.PrintWriter;\n\nimport javax.servlet.ServletException;\nimport javax.servlet.annotation.WebServlet;\nimport javax.servlet.http.HttpServlet;\nimport javax.servlet.http.HttpServletRequest;\nimport javax.servlet.http.HttpServletResponse;\n\n\/**\n * Servlet implementation class AddServlet\n *\/\n@WebServlet(\"\/CalcServlet\")\npublic class CalcServlet extends HttpServlet {\n\tprivate static final long serialVersionUID = 1L;\n       \n    \/**\n     * @see HttpServlet#HttpServlet()\n     *\/\n    public CalcServlet() {\n        super();\n        \/\/ TODO Auto-generated constructor stub\n    }\n\n\t\/**\n\t * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)\n\t *\/\n\tprotected void doGet<\/strong>(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {\n\t\t\/\/ TODO Auto-generated method stub\n\t\t\/\/response.getWriter().append(\"Served at: \").append(request.getContextPath());\n\t\tint num1 = Integer.parseInt(request.getParameter(\"num1\"));\n\t\tint num2 = Integer.parseInt(request.getParameter(\"num2\"));\n\t\t\n\t\tresponse.getWriter().write(String.format(\"%s + %s = %s\", num1, num2, num1+num2));\n\t}\n\n\t\/**\n\t * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)\n\t *\/\n\tprotected void doPost<\/strong>(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {\n\t\t\/\/ TODO Auto-generated method stub\n\t\t\/\/doGet(request, response);\n\t\tint num1 = Integer.parseInt(request.getParameter(\"num1\"));\n\t\tint num2 = Integer.parseInt(request.getParameter(\"num2\"));\n\t\t\n\t\tresponse.getWriter().write(String.format(\"%s * %s = %s\", num1, num2, num1*num2));\n\t}\n\t\n\tprotected void doPut<\/strong>(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {\n\t\t\/\/ TODO Auto-generated method stub\n\t\t\/\/doGet(request, response);\n\t\tint num1 = Integer.parseInt(request.getParameter(\"num1\"));\n\t\tint num2 = Integer.parseInt(request.getParameter(\"num2\"));\n\t\t\n\t\tresponse.getWriter().write(String.format(\"%s - %s = %s\", num1, num2, num1-num2));\n\t}\n\n\tprotected void doDelete<\/strong>(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {\n\t\t\/\/ TODO Auto-generated method stub\n\t\t\/\/doGet(request, response);\n\t\tint num1 = Integer.parseInt(request.getParameter(\"num1\"));\n\t\tint num2 = Integer.parseInt(request.getParameter(\"num2\"));\n\t\t\n\t\tresponse.getWriter().write(String.format(\"%s \/ %s = %s\", num1, num2, num1\/num2));\n\t}\n\n\tprotected void doOptions<\/strong>(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {\n\t\t\/\/ TODO Auto-generated method stub\n\t\t\/\/doGet(request, response);\n\t\tint num1 = Integer.parseInt(request.getParameter(\"num1\"));\n\t\tint num2 = Integer.parseInt(request.getParameter(\"num2\"));\n\t\t\n\t\tresponse.getWriter().write(String.format(\"%s %% %s = %s\", num1, num2, num1%num2));\n\t}\n\n}\n<\/code><\/pre>\n\n\n\n
    DATABASE SQL<\/p>\n\n\n\n
    CREATE DATABASE<\/p>\n\n\n\n
    CREATE DATABASE company;<\/code><\/pre>\n\n\n\n
    CREATE TABLE<\/p>\n\n\n\n
    CREATE TABLE users(\n    id INT,\n    NAME VARCHAR(100) NOT NULL,\n    age TINYINT NOT NULL,\n    city VARCHAR(200) NOT NULL\n);<\/code><\/pre>\n\n\n\n
    ALTER TABLE<\/p>\n\n\n\n
    ALTER TABLE\n    users MODIFY id INT PRIMARY KEY AUTO_INCREMENT;<\/code><\/pre>\n\n\n\n
    MySQL JDBC<\/p>\n\n\n\n
    import java.sql.Connection;\nimport java.sql.DriverManager;\nimport java.sql.ResultSet;\nimport java.sql.Statement;\n\npublic class CRUDLDemo {\n\tpublic static void main(String args[]) {\n\t\tString conn_str = \"jdbc:mysql:\/\/localhost:3306\/company\";\n\t\tString dbusername = \"root\";\n\t\tString dbpassword = \"\";\n\n\t\ttry {\n\t\t\tClass.forName(\"com.mysql.cj.jdbc.Driver\");\n\t\t\tConnection conn = DriverManager.getConnection(conn_str, dbusername, dbpassword);\n\n\t\t\tString select_sql = \"SELECT * FROM users\";\n\t\t\tStatement stmt = conn.createStatement();\n\n\t\t\tResultSet rs = stmt.executeQuery(select_sql);\n\n\t\t\twhile (rs.next()) {\n\t\t\t\tSystem.out.println(rs.getInt(\"id\"));\n\t\t\t\tSystem.out.println(rs.getString(\"name\"));\n\t\t\t\tSystem.out.println(rs.getInt(\"age\"));\n\t\t\t\tSystem.out.println(rs.getString(\"city\"));\n\t\t\t}\n\n\/\/\t\t\tString insert_sql = \"INSERT INTO users VALUES (NULL, 'Priyanka', 30, 'Mumbai', NOW(), NOW())\";\n\/\/\t\t\tStatement stmt = conn.createStatement();\n\/\/\t\t\tint result = stmt.executeUpdate(insert_sql);\n\/\/\t\t\tSystem.out.println(result);\n\n\/\/\t\t\tString delete_sql = \"DELETE FROM users WHERE id = 3\";\n\/\/\t\t\tStatement stmt = conn.createStatement();\n\/\/\t\t\tint result = stmt.executeUpdate(delete_sql);\n\/\/\t\t\tSystem.out.println(result);\n\n\/\/\t\t\tString update_sql = \"UPDATE users SET city = 'Panvel' WHERE id = 2\";\n\/\/\t\t\tStatement stmt = conn.createStatement();\n\/\/\t\t\tint result = stmt.executeUpdate(update_sql);\n\/\/\t\t\tSystem.out.println(result);\n\n\t\t} catch (Exception e) {\n\t\t\te.printStackTrace();\n\t\t}\n\n\t}\n\n}\n<\/code><\/pre>\n\n\n\n
    select.jsp<\/p>\n\n\n\n
    <%@page import=\"java.sql.ResultSet\"%>\n<%@page import=\"java.sql.Statement\"%>\n<%@page import=\"java.sql.DriverManager\"%>\n<%@page import=\"java.sql.Connection\"%>\n<%@ page language=\"java\" contentType=\"text\/html; charset=ISO-8859-1\"\n\tpageEncoding=\"ISO-8859-1\"%>\n<% \n\nString conn_string = \"jdbc:mysql:\/\/localhost:3306\/company\";\nString db_username = \"root\";\nString db_password = \"\";\n\nConnection conn = null;\n\ntry{\n\tClass.forName(\"com.mysql.cj.jdbc.Driver\");\n\tconn = DriverManager.getConnection(conn_string, db_username, db_password);\n} catch(Exception e) {\n\tout.println(e);\n}\n\nString select_sql = \"SELECT * FROM users\";\nStatement stmt = conn.createStatement();\nResultSet rs = stmt.executeQuery(select_sql);\n\nwhile(rs.next()) {\n\tout.println(String.format(\"Id: %s | Name: %s | Age: %s | City: %s<br>\", rs.getInt(\"id\"), rs.getString(\"name\"), rs.getInt(\"age\"), rs.getString(\"city\")));\n}\n\n%><\/code><\/pre>\n\n\n\n
    insert.jsp<\/p>\n\n\n\n
    <%@page import=\"java.sql.Statement\"%>\n<%@page import=\"java.sql.DriverManager\"%>\n<%@page import=\"java.sql.Connection\"%>\n<%\nString conn_string = \"jdbc:mysql:\/\/localhost:3306\/company\";\nString db_username = \"root\";\nString db_password = \"\";\n\nConnection conn = null;\n\ntry{\n\tClass.forName(\"com.mysql.cj.jdbc.Driver\");\n\tconn = DriverManager.getConnection(conn_string, db_username, db_password);\n} catch(Exception e) {\n\tout.println(e);\n}\n\nString insert_sql = \"INSERT INTO users VALUES (NULL, 'Priyanka', 30, 'Mumbai', NOW(), NOW())\";\nStatement stmt = conn.createStatement();\nint result = stmt.executeUpdate(insert_sql);\n\nif(result == 1) {\n\tout.println(\"Record inserted successfully...\");\n} else {\n\tout.println(\"Something went wrong...\");\n}\n%><\/code><\/pre>\n\n\n\n
    update.jsp<\/p>\n\n\n\n
    <%@page import=\"java.sql.Statement\"%>\n<%@page import=\"java.sql.DriverManager\"%>\n<%@page import=\"java.sql.Connection\"%>\n<%\nString conn_string = \"jdbc:mysql:\/\/localhost:3306\/company\";\nString db_username = \"root\";\nString db_password = \"\";\n\nConnection conn = null;\n\ntry{\n\tClass.forName(\"com.mysql.cj.jdbc.Driver\");\n\tconn = DriverManager.getConnection(conn_string, db_username, db_password);\n} catch(Exception e) {\n\tout.println(e);\n}\n\nString update_sql = \"UPDATE users SET name = 'Palkar' WHERE id = 4\";\nStatement stmt = conn.createStatement();\nint result = stmt.executeUpdate(update_sql);\n\nif(result == 1) {\n\tout.println(\"Record updated successfully...\");\n} else {\n\tout.println(\"Something went wrong...\");\n}\n%><\/code><\/pre>\n\n\n\n
    delete.jsp<\/p>\n\n\n\n
    <%@page import=\"java.sql.Statement\"%>\n<%@page import=\"java.sql.DriverManager\"%>\n<%@page import=\"java.sql.Connection\"%>\n<%\nString conn_string = \"jdbc:mysql:\/\/localhost:3306\/company\";\nString db_username = \"root\";\nString db_password = \"\";\n\nConnection conn = null;\n\ntry{\n\tClass.forName(\"com.mysql.cj.jdbc.Driver\");\n\tconn = DriverManager.getConnection(conn_string, db_username, db_password);\n} catch(Exception e) {\n\tout.println(e);\n}\n\nString delete_sql = \"DELETE FROM users WHERE id = 4\";\nStatement stmt = conn.createStatement();\nint result = stmt.executeUpdate(delete_sql);\n\nif(result == 1) {\n\tout.println(\"Record deleted successfully...\");\n} else {\n\tout.println(\"Something went wrong...\");\n}\n%><\/code><\/pre>\n\n\n\n
    functions.jsp<\/p>\n\n\n\n
    <%@page import=\"java.sql.DriverManager\"%>\n<%@page import=\"java.sql.Connection\"%>\n\n<%!\npublic Connection getConnection() {\n\n\t\tString conn_string = \"jdbc:mysql:\/\/localhost:3306\/company\";\n\t\tString db_username = \"root\";\n\t\tString db_password = \"\";\n\n\t\tConnection conn = null;\n\n\t\ttry {\n\t\t\tClass.forName(\"com.mysql.cj.jdbc.Driver\");\n\t\t\tconn = DriverManager.getConnection(conn_string, db_username, db_password);\n\t\t} catch (Exception e) {\n\t\t\tSystem.out.println(e);\n\t\t}\n\n\t\treturn conn;\n}\n\npublic void authorize(HttpSession session, HttpServletResponse response) {\r\n\t\r\n\tif(session.getAttribute(\"username\") == null) {\r\n\t\ttry {\t\t\t\t\r\n\t\t\tresponse.sendRedirect(\"login_form.jsp?msg=Please login to access this page\");\r\n\t\t\t\r\n\t\t} catch(Exception e) {\r\n\t\t\te.printStackTrace();\r\n\t\t}\r\n\t}\r\n}\r\n\n%><\/code><\/pre>\n\n\n\n
    include functions and header<\/p>\n\n\n\n
    <%@include file=\"functions.jsp\" %>\n<jsp:include page=\"header.jsp\" \/><\/code><\/pre>\n\n\n\n
    <\/p>\n","protected":false},"excerpt":{"rendered":"
    Softwares to Install JDK 11https:\/\/www.oracle.com\/in\/java\/technologies\/javase-jdk11-downloads.html Apache Tomcat Server (version 9)https:\/\/tomcat.apache.org\/download-90.cgi Eclipse EE (2021)https:\/\/www.eclipse.org\/downloads\/packages\/release\/neon\/3\/eclipse-ide-java-ee-developers Xampp for MySQL (latest version)https:\/\/www.apachefriends.org\/download.html Postman for REST APIhttps:\/\/www.postman.com\/downloads\/ Addition of Two Numbers Inheritance Exception Handling Servlet Demo Servlet Life Cycle form.html 2. CalcServlet DATABASE SQL CREATE DATABASE CREATE TABLE ALTER TABLE MySQL JDBC select.jsp insert.jsp update.jsp delete.jsp functions.jsp include functions and […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[3],"tags":[],"_links":{"self":[{"href":"https:\/\/codeinsightacademy.com\/blog\/wp-json\/wp\/v2\/posts\/1353"}],"collection":[{"href":"https:\/\/codeinsightacademy.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/codeinsightacademy.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/codeinsightacademy.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/codeinsightacademy.com\/blog\/wp-json\/wp\/v2\/comments?post=1353"}],"version-history":[{"count":20,"href":"https:\/\/codeinsightacademy.com\/blog\/wp-json\/wp\/v2\/posts\/1353\/revisions"}],"predecessor-version":[{"id":1409,"href":"https:\/\/codeinsightacademy.com\/blog\/wp-json\/wp\/v2\/posts\/1353\/revisions\/1409"}],"wp:attachment":[{"href":"https:\/\/codeinsightacademy.com\/blog\/wp-json\/wp\/v2\/media?parent=1353"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/codeinsightacademy.com\/blog\/wp-json\/wp\/v2\/categories?post=1353"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/codeinsightacademy.com\/blog\/wp-json\/wp\/v2\/tags?post=1353"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}