diff --git a/.gitignore b/.gitignore
index 7bec898..b1aeb70 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,11 @@
-# Project exclude paths
-/.gradle/
\ No newline at end of file
+# Gradle files
+.gradle/
+build/
+
+# IntelliJ
+*.iml
+.idea/
+misc.xml
+deploymentTargetDropDown.xml
+render.experimental.xml
+.DS_Store
\ No newline at end of file
diff --git a/.idea/compiler.xml b/.idea/compiler.xml
index fb7f4a8..b589d56 100644
--- a/.idea/compiler.xml
+++ b/.idea/compiler.xml
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
   <component name="CompilerConfiguration">
-    <bytecodeTargetLevel target="11" />
+    <bytecodeTargetLevel target="17" />
   </component>
 </project>
\ No newline at end of file
diff --git a/.idea/gradle.xml b/.idea/gradle.xml
index ba1ec5c..ce1c62c 100644
--- a/.idea/gradle.xml
+++ b/.idea/gradle.xml
@@ -1,9 +1,9 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
+  <component name="GradleMigrationSettings" migrationVersion="1" />
   <component name="GradleSettings">
     <option name="linkedExternalProjectsSettings">
       <GradleProjectSettings>
-        <option name="distributionType" value="DEFAULT_WRAPPED" />
         <option name="externalProjectPath" value="$PROJECT_DIR$" />
         <option name="modules">
           <set>
diff --git a/.idea/kotlinc.xml b/.idea/kotlinc.xml
new file mode 100644
index 0000000..0e65cea
--- /dev/null
+++ b/.idea/kotlinc.xml
@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="KotlinJpsPluginSettings">
+    <option name="version" value="1.7.21" />
+  </component>
+</project>
\ No newline at end of file
diff --git a/.idea/misc.xml b/.idea/misc.xml
index d384b66..f42487a 100644
--- a/.idea/misc.xml
+++ b/.idea/misc.xml
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
   <component name="ExternalStorageConfigurationManager" enabled="true" />
-  <component name="ProjectRootManager" version="2" languageLevel="JDK_11" default="true" project-jdk-name="jbr-11" project-jdk-type="JavaSDK">
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_17" project-jdk-name="openjdk-17" project-jdk-type="JavaSDK">
     <output url="file://$PROJECT_DIR$/out" />
   </component>
 </project>
\ No newline at end of file
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
index 69a9715..ffed3a2 100644
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-7.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.2-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
diff --git a/gradlew b/gradlew
index 744e882..1b6c787 100755
--- a/gradlew
+++ b/gradlew
@@ -1,7 +1,7 @@
-#!/usr/bin/env sh
+#!/bin/sh
 
 #
-# Copyright 2015 the original author or authors.
+# Copyright © 2015-2021 the original authors.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -17,67 +17,101 @@
 #
 
 ##############################################################################
-##
-##  Gradle start up script for UN*X
-##
+#
+#   Gradle start up script for POSIX generated by Gradle.
+#
+#   Important for running:
+#
+#   (1) You need a POSIX-compliant shell to run this script. If your /bin/sh is
+#       noncompliant, but you have some other compliant shell such as ksh or
+#       bash, then to run this script, type that shell name before the whole
+#       command line, like:
+#
+#           ksh Gradle
+#
+#       Busybox and similar reduced shells will NOT work, because this script
+#       requires all of these POSIX shell features:
+#         * functions;
+#         * expansions «$var», «${var}», «${var:-default}», «${var+SET}»,
+#           «${var#prefix}», «${var%suffix}», and «$( cmd )»;
+#         * compound commands having a testable exit status, especially «case»;
+#         * various built-in commands including «command», «set», and «ulimit».
+#
+#   Important for patching:
+#
+#   (2) This script targets any POSIX shell, so it avoids extensions provided
+#       by Bash, Ksh, etc; in particular arrays are avoided.
+#
+#       The "traditional" practice of packing multiple parameters into a
+#       space-separated string is a well documented source of bugs and security
+#       problems, so this is (mostly) avoided, by progressively accumulating
+#       options in "$@", and eventually passing that to Java.
+#
+#       Where the inherited environment variables (DEFAULT_JVM_OPTS, JAVA_OPTS,
+#       and GRADLE_OPTS) rely on word-splitting, this is performed explicitly;
+#       see the in-line comments for details.
+#
+#       There are tweaks for specific operating systems such as AIX, CygWin,
+#       Darwin, MinGW, and NonStop.
+#
+#   (3) This script is generated from the Groovy template
+#       https://github.com/gradle/gradle/blob/master/subprojects/plugins/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
+#       within the Gradle project.
+#
+#       You can find Gradle at https://github.com/gradle/gradle/.
+#
 ##############################################################################
 
 # Attempt to set APP_HOME
+
 # Resolve links: $0 may be a link
-PRG="$0"
-# Need this for relative symlinks.
-while [ -h "$PRG" ] ; do
-    ls=`ls -ld "$PRG"`
-    link=`expr "$ls" : '.*-> \(.*\)$'`
-    if expr "$link" : '/.*' > /dev/null; then
-        PRG="$link"
-    else
-        PRG=`dirname "$PRG"`"/$link"
-    fi
+app_path=$0
+
+# Need this for daisy-chained symlinks.
+while
+    APP_HOME=${app_path%"${app_path##*/}"}  # leaves a trailing /; empty if no leading path
+    [ -h "$app_path" ]
+do
+    ls=$( ls -ld "$app_path" )
+    link=${ls#*' -> '}
+    case $link in             #(
+      /*)   app_path=$link ;; #(
+      *)    app_path=$APP_HOME$link ;;
+    esac
 done
-SAVED="`pwd`"
-cd "`dirname \"$PRG\"`/" >/dev/null
-APP_HOME="`pwd -P`"
-cd "$SAVED" >/dev/null
+
+APP_HOME=$( cd "${APP_HOME:-./}" && pwd -P ) || exit
 
 APP_NAME="Gradle"
-APP_BASE_NAME=`basename "$0"`
+APP_BASE_NAME=${0##*/}
 
 # Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
 DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
 
 # Use the maximum available, or set MAX_FD != -1 to use that value.
-MAX_FD="maximum"
+MAX_FD=maximum
 
 warn () {
     echo "$*"
-}
+} >&2
 
 die () {
     echo
     echo "$*"
     echo
     exit 1
-}
+} >&2
 
 # OS specific support (must be 'true' or 'false').
 cygwin=false
 msys=false
 darwin=false
 nonstop=false
-case "`uname`" in
-  CYGWIN* )
-    cygwin=true
-    ;;
-  Darwin* )
-    darwin=true
-    ;;
-  MSYS* | MINGW* )
-    msys=true
-    ;;
-  NONSTOP* )
-    nonstop=true
-    ;;
+case "$( uname )" in                #(
+  CYGWIN* )         cygwin=true  ;; #(
+  Darwin* )         darwin=true  ;; #(
+  MSYS* | MINGW* )  msys=true    ;; #(
+  NONSTOP* )        nonstop=true ;;
 esac
 
 CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
@@ -87,9 +121,9 @@ CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
 if [ -n "$JAVA_HOME" ] ; then
     if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
         # IBM's JDK on AIX uses strange locations for the executables
-        JAVACMD="$JAVA_HOME/jre/sh/java"
+        JAVACMD=$JAVA_HOME/jre/sh/java
     else
-        JAVACMD="$JAVA_HOME/bin/java"
+        JAVACMD=$JAVA_HOME/bin/java
     fi
     if [ ! -x "$JAVACMD" ] ; then
         die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
@@ -98,7 +132,7 @@ Please set the JAVA_HOME variable in your environment to match the
 location of your Java installation."
     fi
 else
-    JAVACMD="java"
+    JAVACMD=java
     which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
 
 Please set the JAVA_HOME variable in your environment to match the
@@ -106,80 +140,95 @@ location of your Java installation."
 fi
 
 # Increase the maximum file descriptors if we can.
-if [ "$cygwin" = "false" -a "$darwin" = "false" -a "$nonstop" = "false" ] ; then
-    MAX_FD_LIMIT=`ulimit -H -n`
-    if [ $? -eq 0 ] ; then
-        if [ "$MAX_FD" = "maximum" -o "$MAX_FD" = "max" ] ; then
-            MAX_FD="$MAX_FD_LIMIT"
-        fi
-        ulimit -n $MAX_FD
-        if [ $? -ne 0 ] ; then
-            warn "Could not set maximum file descriptor limit: $MAX_FD"
-        fi
-    else
-        warn "Could not query maximum file descriptor limit: $MAX_FD_LIMIT"
-    fi
+if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
+    case $MAX_FD in #(
+      max*)
+        MAX_FD=$( ulimit -H -n ) ||
+            warn "Could not query maximum file descriptor limit"
+    esac
+    case $MAX_FD in  #(
+      '' | soft) :;; #(
+      *)
+        ulimit -n "$MAX_FD" ||
+            warn "Could not set maximum file descriptor limit to $MAX_FD"
+    esac
 fi
 
-# For Darwin, add options to specify how the application appears in the dock
-if $darwin; then
-    GRADLE_OPTS="$GRADLE_OPTS \"-Xdock:name=$APP_NAME\" \"-Xdock:icon=$APP_HOME/media/gradle.icns\""
-fi
+# Collect all arguments for the java command, stacking in reverse order:
+#   * args from the command line
+#   * the main class name
+#   * -classpath
+#   * -D...appname settings
+#   * --module-path (only if needed)
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, and GRADLE_OPTS environment variables.
 
 # For Cygwin or MSYS, switch paths to Windows format before running java
-if [ "$cygwin" = "true" -o "$msys" = "true" ] ; then
-    APP_HOME=`cygpath --path --mixed "$APP_HOME"`
-    CLASSPATH=`cygpath --path --mixed "$CLASSPATH"`
-
-    JAVACMD=`cygpath --unix "$JAVACMD"`
-
-    # We build the pattern for arguments to be converted via cygpath
-    ROOTDIRSRAW=`find -L / -maxdepth 1 -mindepth 1 -type d 2>/dev/null`
-    SEP=""
-    for dir in $ROOTDIRSRAW ; do
-        ROOTDIRS="$ROOTDIRS$SEP$dir"
-        SEP="|"
-    done
-    OURCYGPATTERN="(^($ROOTDIRS))"
-    # Add a user-defined pattern to the cygpath arguments
-    if [ "$GRADLE_CYGPATTERN" != "" ] ; then
-        OURCYGPATTERN="$OURCYGPATTERN|($GRADLE_CYGPATTERN)"
-    fi
+if "$cygwin" || "$msys" ; then
+    APP_HOME=$( cygpath --path --mixed "$APP_HOME" )
+    CLASSPATH=$( cygpath --path --mixed "$CLASSPATH" )
+
+    JAVACMD=$( cygpath --unix "$JAVACMD" )
+
     # Now convert the arguments - kludge to limit ourselves to /bin/sh
-    i=0
-    for arg in "$@" ; do
-        CHECK=`echo "$arg"|egrep -c "$OURCYGPATTERN" -`
-        CHECK2=`echo "$arg"|egrep -c "^-"`                                 ### Determine if an option
-
-        if [ $CHECK -ne 0 ] && [ $CHECK2 -eq 0 ] ; then                    ### Added a condition
-            eval `echo args$i`=`cygpath --path --ignore --mixed "$arg"`
-        else
-            eval `echo args$i`="\"$arg\""
+    for arg do
+        if
+            case $arg in                                #(
+              -*)   false ;;                            # don't mess with options #(
+              /?*)  t=${arg#/} t=/${t%%/*}              # looks like a POSIX filepath
+                    [ -e "$t" ] ;;                      #(
+              *)    false ;;
+            esac
+        then
+            arg=$( cygpath --path --ignore --mixed "$arg" )
         fi
-        i=`expr $i + 1`
+        # Roll the args list around exactly as many times as the number of
+        # args, so each arg winds up back in the position where it started, but
+        # possibly modified.
+        #
+        # NB: a `for` loop captures its iteration list before it begins, so
+        # changing the positional parameters here affects neither the number of
+        # iterations, nor the values presented in `arg`.
+        shift                   # remove old arg
+        set -- "$@" "$arg"      # push replacement arg
     done
-    case $i in
-        0) set -- ;;
-        1) set -- "$args0" ;;
-        2) set -- "$args0" "$args1" ;;
-        3) set -- "$args0" "$args1" "$args2" ;;
-        4) set -- "$args0" "$args1" "$args2" "$args3" ;;
-        5) set -- "$args0" "$args1" "$args2" "$args3" "$args4" ;;
-        6) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" ;;
-        7) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" ;;
-        8) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" ;;
-        9) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" "$args8" ;;
-    esac
 fi
 
-# Escape application args
-save () {
-    for i do printf %s\\n "$i" | sed "s/'/'\\\\''/g;1s/^/'/;\$s/\$/' \\\\/" ; done
-    echo " "
-}
-APP_ARGS=`save "$@"`
+# Collect all arguments for the java command;
+#   * $DEFAULT_JVM_OPTS, $JAVA_OPTS, and $GRADLE_OPTS can contain fragments of
+#     shell script including quotes and variable substitutions, so put them in
+#     double quotes to make sure that they get re-expanded; and
+#   * put everything else in single quotes, so that it's not re-expanded.
+
+set -- \
+        "-Dorg.gradle.appname=$APP_BASE_NAME" \
+        -classpath "$CLASSPATH" \
+        org.gradle.wrapper.GradleWrapperMain \
+        "$@"
+
+# Use "xargs" to parse quoted args.
+#
+# With -n1 it outputs one arg per line, with the quotes and backslashes removed.
+#
+# In Bash we could simply go:
+#
+#   readarray ARGS < <( xargs -n1 <<<"$var" ) &&
+#   set -- "${ARGS[@]}" "$@"
+#
+# but POSIX shell has neither arrays nor command substitution, so instead we
+# post-process each arg (as a line of input to sed) to backslash-escape any
+# character that might be a shell metacharacter, then use eval to reverse
+# that process (while maintaining the separation between arguments), and wrap
+# the whole thing up as a single "set" statement.
+#
+# This will of course break if any of these variables contains a newline or
+# an unmatched quote.
+#
 
-# Collect all arguments for the java command, following the shell quoting and substitution rules
-eval set -- $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS "\"-Dorg.gradle.appname=$APP_BASE_NAME\"" -classpath "\"$CLASSPATH\"" org.gradle.wrapper.GradleWrapperMain "$APP_ARGS"
+eval "set -- $(
+        printf '%s\n' "$DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS" |
+        xargs -n1 |
+        sed ' s~[^-[:alnum:]+,./:=@_]~\\&~g; ' |
+        tr '\n' ' '
+    )" '"$@"'
 
 exec "$JAVACMD" "$@"
diff --git a/src/main/kotlin/Main.kt b/src/main/kotlin/Main.kt
new file mode 100644
index 0000000..983c7a9
--- /dev/null
+++ b/src/main/kotlin/Main.kt
@@ -0,0 +1,63 @@
+import builder.Customer
+import builder.CustomerBuilderImpl
+import builder.Status
+import command.*
+import decorator.CompanyMemberDecorator
+import decorator.VipCustomerDecorator
+import singleton.DataBase
+import singleton.DataBaseLazyThreadSafeImpl
+import singleton.DataBaseSimpleImpl
+import singleton.DataBaseThreadSafeImpl
+
+fun main() {
+
+    val sasha: Customer = CustomerBuilderImpl().setName("Sasha").setAge(33).build()
+    val natasha: Customer = CustomerBuilderImpl().setName("Natasha").setAge(44).build()
+    val pasha: Customer = CustomerBuilderImpl().setName("Pasha").setStatus(Status.Gold).build()
+    val dasha: Customer = CustomerBuilderImpl().setName("Dasha").setAge(23).setStatus(Status.Silver).build()
+
+    val dbSimple: DataBase<Customer> = DataBaseSimpleImpl.INSTANCE
+    val dbThreadSafe: DataBase<Customer> = DataBaseThreadSafeImpl.getInstance()
+
+    val commandsList =
+        listOf(InsertCommand(dbSimple,sasha),
+            InsertCommand(dbSimple,pasha),
+            InsertCommand(dbSimple,dasha),
+            UpdateCommand(dbSimple, Customer(sasha.id, "SASHA", 34, Status.Silver)),
+            SelectCommand(dbSimple, sasha.id),
+            InsertCommand(dbThreadSafe, natasha),
+            InsertCommand(dbThreadSafe,dasha),
+            DeleteCommand(dbThreadSafe, natasha.id))
+
+    commandsList.forEach { command -> command.execute() }
+
+    val productPrice = 400
+    val anotherProductPrice = 30
+
+    val sergeyPetrovich = CustomerBuilderImpl().setName("Sergey Petrovich").setAge(66).setStatus(Status.Platinum).build()
+    println("sergeyPetrovich price: ${sergeyPetrovich.applyPersonalDiscount(productPrice)}")
+    val vipSergeyPetrovich = VipCustomerDecorator(sergeyPetrovich)
+    println("vipSergeyPetrovich price: ${vipSergeyPetrovich.applyPersonalDiscount(productPrice)}")
+
+    val kolyaTheCompanyMember = CompanyMemberDecorator(CustomerBuilderImpl().setName("Kolya").build())
+    println("KolyaTheMember product price ${kolyaTheCompanyMember.applyPersonalDiscount(productPrice)}")
+    println("KolyaTheMember current bonus: ${kolyaTheCompanyMember.memberBonus}")
+
+    val priceReducedByBonus = kolyaTheCompanyMember.spendBonus(anotherProductPrice)
+    println("KolyaTheMember another product price $anotherProductPrice ReducedByBonus = $priceReducedByBonus")
+    println("KolyaTheMember current bonus: ${kolyaTheCompanyMember.memberBonus}")
+
+
+    val dbLazyThreadSafeImpl = DataBaseLazyThreadSafeImpl.INSTANCE
+    val newCommandsList =
+        listOf(InsertCommand(dbLazyThreadSafeImpl,sasha),
+            InsertCommand(dbLazyThreadSafeImpl,pasha),
+            InsertCommand(dbLazyThreadSafeImpl,dasha),
+            UpdateCommand(dbLazyThreadSafeImpl, Customer(dasha.id, "DARIA", 24, Status.Gold)),
+            SelectCommand(dbLazyThreadSafeImpl, dasha.id),
+            InsertCommand(dbLazyThreadSafeImpl, natasha),
+            DeleteCommand(dbLazyThreadSafeImpl, sasha.id))
+
+    newCommandsList.forEach { command -> command.execute() }
+    dbLazyThreadSafeImpl.list.forEach {customer -> println(customer)}
+}
\ No newline at end of file
diff --git a/src/main/kotlin/builder/Customer.kt b/src/main/kotlin/builder/Customer.kt
new file mode 100644
index 0000000..67ad9b1
--- /dev/null
+++ b/src/main/kotlin/builder/Customer.kt
@@ -0,0 +1,17 @@
+package builder
+
+data class Customer(
+    val id: Int = 0,
+    val name: String,
+    val age: Int? = null,
+    val status: Status? = null
+) : CustomerDiscountCalculator {
+    override fun applyPersonalDiscount(price: Int): Int {
+        return when (status) {
+            is Status.Silver -> (price - (price * status.discount)).toInt()
+            is Status.Gold -> (price - (price * status.discount)).toInt()
+            is Status.Platinum -> (price - (price * status.discount)).toInt()
+            else -> price
+        }
+    }
+}
diff --git a/src/main/kotlin/builder/CustomerBuilder.kt b/src/main/kotlin/builder/CustomerBuilder.kt
new file mode 100644
index 0000000..49195c2
--- /dev/null
+++ b/src/main/kotlin/builder/CustomerBuilder.kt
@@ -0,0 +1,9 @@
+package builder
+
+
+interface CustomerBuilder {
+    fun build(): Customer
+    fun setName(name: String): CustomerBuilder
+    fun setAge(age: Int): CustomerBuilder
+    fun setStatus(status: Status): CustomerBuilder
+}
\ No newline at end of file
diff --git a/src/main/kotlin/builder/CustomerBuilderImpl.kt b/src/main/kotlin/builder/CustomerBuilderImpl.kt
new file mode 100644
index 0000000..0f52ab6
--- /dev/null
+++ b/src/main/kotlin/builder/CustomerBuilderImpl.kt
@@ -0,0 +1,36 @@
+package builder
+
+class CustomerBuilderImpl : CustomerBuilder {
+
+    private var _name: String = DEFAULT_NAME
+    private var _age: Int? = null
+    private var _status: Status? = Status.NewCustomer
+
+    override fun build(): Customer {
+        return Customer(++id, _name, _age, _status)
+    }
+
+    override fun setName(name: String): CustomerBuilderImpl {
+        _name = name
+        return this
+    }
+
+    override fun setAge(age: Int): CustomerBuilderImpl {
+        if (age < MIN_AGE) {
+            error("Invalid argument")
+        }
+        _age = age
+        return this
+    }
+
+    override fun setStatus(status: Status): CustomerBuilderImpl {
+        _status = status
+        return this
+    }
+
+    companion object {
+        private var id: Int = 0
+        private const val DEFAULT_NAME: String = "New customer"
+        private const val MIN_AGE = 18
+    }
+}
\ No newline at end of file
diff --git a/src/main/kotlin/builder/CustomerDiscountCalculator.kt b/src/main/kotlin/builder/CustomerDiscountCalculator.kt
new file mode 100644
index 0000000..9685954
--- /dev/null
+++ b/src/main/kotlin/builder/CustomerDiscountCalculator.kt
@@ -0,0 +1,5 @@
+package builder
+
+interface CustomerDiscountCalculator {
+    fun applyPersonalDiscount(price: Int): Int
+}
\ No newline at end of file
diff --git a/src/main/kotlin/builder/Status.kt b/src/main/kotlin/builder/Status.kt
new file mode 100644
index 0000000..12c54fc
--- /dev/null
+++ b/src/main/kotlin/builder/Status.kt
@@ -0,0 +1,8 @@
+package builder
+
+sealed class Status {
+    object NewCustomer: Status()
+    object Silver: Status() {const val discount: Double = 0.05}
+    object Gold: Status() {const val discount: Double = 0.10}
+    object Platinum: Status() {const val discount: Double = 0.15}
+}
\ No newline at end of file
diff --git a/src/main/kotlin/command/Command.kt b/src/main/kotlin/command/Command.kt
new file mode 100644
index 0000000..c16d907
--- /dev/null
+++ b/src/main/kotlin/command/Command.kt
@@ -0,0 +1,5 @@
+package command
+
+interface Command<R> {
+    fun execute(): R
+}
\ No newline at end of file
diff --git a/src/main/kotlin/command/DeleteCommand.kt b/src/main/kotlin/command/DeleteCommand.kt
new file mode 100644
index 0000000..c940853
--- /dev/null
+++ b/src/main/kotlin/command/DeleteCommand.kt
@@ -0,0 +1,13 @@
+package command
+
+import builder.Customer
+import singleton.DataBase
+
+class DeleteCommand (
+    private val dataBase: DataBase<Customer>,
+    private val id: Int
+) : Command<Unit> {
+    override fun execute() {
+        dataBase.delete(id)
+    }
+}
\ No newline at end of file
diff --git a/src/main/kotlin/command/InsertCommand.kt b/src/main/kotlin/command/InsertCommand.kt
new file mode 100644
index 0000000..1cc9f93
--- /dev/null
+++ b/src/main/kotlin/command/InsertCommand.kt
@@ -0,0 +1,13 @@
+package command
+
+import builder.Customer
+import singleton.DataBase
+
+class InsertCommand(
+    private val dataBase: DataBase<Customer>,
+    private val item: Customer
+) : Command<Unit> {
+    override fun execute() {
+        dataBase.insert(item)
+    }
+}
\ No newline at end of file
diff --git a/src/main/kotlin/command/SelectCommand.kt b/src/main/kotlin/command/SelectCommand.kt
new file mode 100644
index 0000000..854bb92
--- /dev/null
+++ b/src/main/kotlin/command/SelectCommand.kt
@@ -0,0 +1,13 @@
+package command
+
+import builder.Customer
+import singleton.DataBase
+
+class SelectCommand (
+    private val dataBase: DataBase<Customer>,
+    private val id: Int
+) : Command<Customer> {
+    override fun execute(): Customer {
+        return dataBase.select(id)
+    }
+}
\ No newline at end of file
diff --git a/src/main/kotlin/command/UpdateCommand.kt b/src/main/kotlin/command/UpdateCommand.kt
new file mode 100644
index 0000000..441d7d8
--- /dev/null
+++ b/src/main/kotlin/command/UpdateCommand.kt
@@ -0,0 +1,13 @@
+package command
+
+import builder.Customer
+import singleton.DataBase
+
+class UpdateCommand (
+    private val dataBase: DataBase<Customer>,
+    private val item: Customer
+) : Command<Unit> {
+    override fun execute() {
+        dataBase.update(item)
+    }
+}
\ No newline at end of file
diff --git a/src/main/kotlin/decorator/CompanyMemberDecorator.kt b/src/main/kotlin/decorator/CompanyMemberDecorator.kt
new file mode 100644
index 0000000..5eae6bf
--- /dev/null
+++ b/src/main/kotlin/decorator/CompanyMemberDecorator.kt
@@ -0,0 +1,34 @@
+package decorator
+
+import builder.CustomerDiscountCalculator
+
+class CompanyMemberDecorator(
+    customer: CustomerDiscountCalculator
+) : CustomerDecorator(customer) {
+
+    private val onEachPurchaseBonusSize = 0.10
+
+    private var _memberBonus: Int = 0
+    val memberBonus
+        get() = _memberBonus
+
+    override fun applyPersonalDiscount(price: Int): Int {
+        getBonus(price)
+        return super.applyPersonalDiscount(price)
+    }
+
+    fun spendBonus(price: Int): Int {
+        var newPrice = 0
+            if (price >= _memberBonus) {
+                newPrice = price - _memberBonus
+                _memberBonus = 0
+            } else {
+                _memberBonus -= price
+            }
+        return newPrice
+    }
+
+    private fun getBonus(purchasePrice: Int) {
+        _memberBonus += (purchasePrice * onEachPurchaseBonusSize).toInt()
+    }
+}
\ No newline at end of file
diff --git a/src/main/kotlin/decorator/CustomerDecorator.kt b/src/main/kotlin/decorator/CustomerDecorator.kt
new file mode 100644
index 0000000..2a16690
--- /dev/null
+++ b/src/main/kotlin/decorator/CustomerDecorator.kt
@@ -0,0 +1,12 @@
+package decorator
+
+import builder.CustomerDiscountCalculator
+
+abstract class CustomerDecorator(
+    private val customer: CustomerDiscountCalculator
+) : CustomerDiscountCalculator {
+
+    override fun applyPersonalDiscount(price: Int): Int {
+        return customer.applyPersonalDiscount(price)
+    }
+}
\ No newline at end of file
diff --git a/src/main/kotlin/decorator/VipCustomerDecorator.kt b/src/main/kotlin/decorator/VipCustomerDecorator.kt
new file mode 100644
index 0000000..afb6669
--- /dev/null
+++ b/src/main/kotlin/decorator/VipCustomerDecorator.kt
@@ -0,0 +1,18 @@
+package decorator
+
+import builder.CustomerDiscountCalculator
+
+class VipCustomerDecorator(
+    customer: CustomerDiscountCalculator
+) : CustomerDecorator(customer) {
+
+    private val vipAdditionalDiscount: Double = 0.10
+
+    override fun applyPersonalDiscount(price: Int): Int {
+        return super.applyPersonalDiscount(applyVipDiscount(price))
+    }
+
+    private fun applyVipDiscount(price: Int): Int {
+        return (price - price * vipAdditionalDiscount).toInt()
+    }
+}
\ No newline at end of file
diff --git a/src/main/kotlin/singleton/DataBase.kt b/src/main/kotlin/singleton/DataBase.kt
new file mode 100644
index 0000000..9970a5e
--- /dev/null
+++ b/src/main/kotlin/singleton/DataBase.kt
@@ -0,0 +1,9 @@
+package singleton
+
+interface DataBase<T> {
+    fun insert(item: T)
+    fun delete(id: Int)
+    fun update(item: T)
+    fun select(id: Int): T
+}
+
diff --git a/src/main/kotlin/singleton/DataBaseLazyThreadSafeImpl.kt b/src/main/kotlin/singleton/DataBaseLazyThreadSafeImpl.kt
new file mode 100644
index 0000000..75e5e41
--- /dev/null
+++ b/src/main/kotlin/singleton/DataBaseLazyThreadSafeImpl.kt
@@ -0,0 +1,43 @@
+package singleton
+
+import builder.Customer
+
+class DataBaseLazyThreadSafeImpl private constructor() : DataBase<Customer> {
+
+    private var _list: MutableList<Customer> = mutableListOf()
+    val list: List<Customer> get() = _list
+
+    override fun insert(item: Customer) {
+        if (_list.add(item)) {
+            println("DataBaseSimple: $item inserted")
+        }
+    }
+
+    override fun delete(id: Int) {
+        _list = _list.filter { customer -> customer.id != id }.toMutableList()
+        println("DataBaseSimple: item with id $id deleted")
+    }
+
+    override fun update(item: Customer) {
+        val newList = _list.map { customer ->
+            if (customer.id == item.id)
+                customer.copy(
+                    customer.id,
+                    item.name,
+                    item.age,
+                    item.status
+                )
+            else customer
+        }
+        _list = newList.toMutableList()
+        println("DataBaseSimple: $item updated")
+    }
+
+    override fun select(id: Int): Customer {
+        return _list.find { customer -> customer.id == id } ?: error("Customer not found")
+    }
+
+    companion object {
+        val INSTANCE: DataBaseLazyThreadSafeImpl by lazy(LazyThreadSafetyMode.SYNCHRONIZED) { DataBaseLazyThreadSafeImpl() }
+    }
+}
\ No newline at end of file
diff --git a/src/main/kotlin/singleton/DataBaseSimpleImpl.kt b/src/main/kotlin/singleton/DataBaseSimpleImpl.kt
new file mode 100644
index 0000000..ad6cff8
--- /dev/null
+++ b/src/main/kotlin/singleton/DataBaseSimpleImpl.kt
@@ -0,0 +1,43 @@
+package singleton
+
+import builder.Customer
+
+class DataBaseSimpleImpl private constructor() : DataBase<Customer> {
+
+    private var list: MutableList<Customer> = mutableListOf()
+
+    override fun insert(item: Customer) {
+        if (list.add(item)) {
+            println("DataBaseSimple: $item inserted")
+        }
+    }
+
+    override fun delete(id: Int) {
+        list = list.filter { customer -> customer.id != id }.toMutableList()
+        println("DataBaseSimple: item with id $id deleted")
+    }
+
+    override fun update(item: Customer) {
+        val newList = list.map { customer ->
+            if (customer.id == item.id)
+                customer.copy(
+                    customer.id,
+                    item.name,
+                    item.age,
+                    item.status
+                )
+            else customer
+        }
+        list = newList.toMutableList()
+        println("DataBaseSimple: $item updated")
+    }
+
+    override fun select(id: Int): Customer {
+        return list.find { customer -> customer.id == id } ?: error("Customer not found")
+    }
+
+    companion object {
+
+        val INSTANCE: DataBaseSimpleImpl by lazy { DataBaseSimpleImpl() }
+    }
+}
\ No newline at end of file
diff --git a/src/main/kotlin/singleton/DataBaseThreadSafeImpl.kt b/src/main/kotlin/singleton/DataBaseThreadSafeImpl.kt
new file mode 100644
index 0000000..2942981
--- /dev/null
+++ b/src/main/kotlin/singleton/DataBaseThreadSafeImpl.kt
@@ -0,0 +1,51 @@
+package singleton
+
+import builder.Customer
+
+class DataBaseThreadSafeImpl private constructor() : DataBase<Customer> {
+
+    private var list: MutableList<Customer> = mutableListOf()
+
+    override fun insert(item: Customer) {
+        if (list.add(item)) {
+            println("DataBaseThreadSafe: $item inserted")
+        }
+    }
+
+    override fun delete(id: Int) {
+        list = list.filter { customer -> customer.id != id }.toMutableList()
+        println("DataBaseThreadSafe: item with id $id deleted")
+    }
+
+    override fun update(item: Customer) {
+        val newList = list.map { customer ->
+            if (customer.id == item.id)
+                customer.copy(
+                    customer.id,
+                    item.name,
+                    item.age,
+                    item.status
+                )
+            else customer
+        }
+        list = newList.toMutableList()
+        println("DataBaseThreadSafe: $item updated")
+    }
+
+    override fun select(id: Int): Customer {
+        return list.find { customer -> customer.id == id } ?: error("Customer not found")
+    }
+
+    companion object {
+        @Volatile
+        private var instance: DataBaseThreadSafeImpl? = null
+
+        fun getInstance(): DataBaseThreadSafeImpl {
+            return instance ?: synchronized(DataBaseThreadSafeImpl) {
+                instance ?: DataBaseThreadSafeImpl().also { dataBase ->
+                    instance = dataBase
+                }
+            }
+        }
+    }
+}
\ No newline at end of file