solution for smart bank

.editorconfig

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+root = true
+
+[*]
+charset = utf-8
+indent_style = space
+
+[*.java]
+indent_size = 2
+insert_final_newline = true

.gitignore

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+.vscode/
+.gradle/
+build/

README.md

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+# VL-PAR-PROG

VL03-02-01/build.gradle

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+apply plugin: 'java'
+
+apply plugin: 'eclipse'
+// Run 'gradlew eclipse' for the eclipse project
+
+apply plugin: 'idea'
+// Run 'gradle idea' for the IntelliJ idea project (no longer necessary in idea 13)
+
+// Netbeans: See http://plugins.netbeans.org/plugin/44510/gradle-support
+
+
+repositories {
+  mavenCentral()
+}
+
+
+dependencies {
+  implementation 'commons-lang:commons-lang:2.6'
+  testImplementation 'junit:junit:4.11'
+  testImplementation 'org.easytesting:fest-assert:1.4'
+}
+

VL03-02-01/gradle/wrapper/gradle-wrapper.properties

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+#Sun Mar 15 22:48:49 CET 2015
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.4-bin.zip

VL03-02-01/gradlew

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+#!/usr/bin/env bash
+
+##############################################################################
+##
+##  Gradle start up script for UN*X
+##
+##############################################################################
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS=""
+
+APP_NAME="Gradle"
+APP_BASE_NAME=`basename "$0"`
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD="maximum"
+
+warn ( ) {
+    echo "$*"
+}
+
+die ( ) {
+    echo
+    echo "$*"
+    echo
+    exit 1
+}
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+case "`uname`" in
+  CYGWIN* )
+    cygwin=true
+    ;;
+  Darwin* )
+    darwin=true
+    ;;
+  MINGW* )
+    msys=true
+    ;;
+esac
+
+# For Cygwin, ensure paths are in UNIX format before anything is touched.
+if $cygwin ; then
+    [ -n "$JAVA_HOME" ] && JAVA_HOME=`cygpath --unix "$JAVA_HOME"`
+fi
+
+# 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"`"/$link"
+    fi
+done
+SAVED="`pwd`"
+cd "`dirname \"$PRG\"`/" >&-
+APP_HOME="`pwd -P`"
+cd "$SAVED" >&-
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+# Determine the Java command to use to start the JVM.
+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="$JAVA_HOME/jre/sh/java"
+    else
+        JAVACMD="$JAVA_HOME/bin/java"
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD="java"
+    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+fi
+
+# Increase the maximum file descriptors if we can.
+if [ "$cygwin" = "false" -a "$darwin" = "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
+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
+
+# For Cygwin, switch paths to Windows format before running java
+if $cygwin ; then
+    APP_HOME=`cygpath --path --mixed "$APP_HOME"`
+    CLASSPATH=`cygpath --path --mixed "$CLASSPATH"`
+
+    # 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
+    # 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`="\"$arg\""
+        fi
+        i=$((i+1))
+    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
+
+# Split up the JVM_OPTS And GRADLE_OPTS values into an array, following the shell quoting and substitution rules
+function splitJvmOpts() {
+    JVM_OPTS=("$@")
+}
+eval splitJvmOpts $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS
+JVM_OPTS[${#JVM_OPTS[*]}]="-Dorg.gradle.appname=$APP_BASE_NAME"
+
+exec "$JAVACMD" "${JVM_OPTS[@]}" -classpath "$CLASSPATH" org.gradle.wrapper.GradleWrapperMain "$@"

VL03-02-01/gradlew.bat

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+@if "%DEBUG%" == "" @echo off
+@rem ##########################################################################
+@rem
+@rem  Gradle startup script for Windows
+@rem
+@rem ##########################################################################
+
+@rem Set local scope for the variables with windows NT shell
+if "%OS%"=="Windows_NT" setlocal
+
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS=
+
+set DIRNAME=%~dp0
+if "%DIRNAME%" == "" set DIRNAME=.
+set APP_BASE_NAME=%~n0
+set APP_HOME=%DIRNAME%
+
+@rem Find java.exe
+if defined JAVA_HOME goto findJavaFromJavaHome
+
+set JAVA_EXE=java.exe
+%JAVA_EXE% -version >NUL 2>&1
+if "%ERRORLEVEL%" == "0" goto init
+
+echo.
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto init
+
+echo.
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:init
+@rem Get command-line arguments, handling Windowz variants
+
+if not "%OS%" == "Windows_NT" goto win9xME_args
+if "%@eval[2+2]" == "4" goto 4NT_args
+
+:win9xME_args
+@rem Slurp the command line arguments.
+set CMD_LINE_ARGS=
+set _SKIP=2
+
+:win9xME_args_slurp
+if "x%~1" == "x" goto execute
+
+set CMD_LINE_ARGS=%*
+goto execute
+
+:4NT_args
+@rem Get arguments from the 4NT Shell from JP Software
+set CMD_LINE_ARGS=%$
+
+:execute
+@rem Setup the command line
+
+set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
+
+@rem Execute Gradle
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %CMD_LINE_ARGS%
+
+:end
+@rem End local scope for the variables with windows NT shell
+if "%ERRORLEVEL%"=="0" goto mainEnd
+
+:fail
+rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
+rem the _cmd.exe /c_ return code!
+if  not "" == "%GRADLE_EXIT_CONSOLE%" exit 1
+exit /b 1
+
+:mainEnd
+if "%OS%"=="Windows_NT" endlocal
+
+:omega

VL03-02-01/src/main/java/de/dhbw/parprog/Account.java

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+package de.dhbw.parprog;
+
+/**
+ * Class which represents a bank account.
+ */
+public class Account {
+
+  /**
+   * The lower limit of the balance.
+   */
+  public static final long LOWER_LIMIT = 0;
+
+  /**
+   * The upper limit of the balance.
+   */
+  public static final long UPPER_LIMIT = 100000;
+
+  /**
+   * The balance of the bank account.
+   */
+  public long balance = 0;
+
+  /**
+   * The bank account number.
+   */
+  public long number = 0;
+  
+  /**
+   * Constructor to create a new bank account.
+   * @param number The bank account number.
+   * @param balance The initial balance of the bank account.
+   */
+  public Account(long number, long balance) {
+    this.balance = balance;
+    this.number = number;
+  }
+}

VL03-02-01/src/main/java/de/dhbw/parprog/Bank.java

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+package de.dhbw.parprog;
+
+/**
+ * Class which represents a bank.
+ */
+public class Bank {
+
+  /**
+   * The next bank account number which can be used for a new bank account.
+   * This number is used to get distinct bank account numbers.
+   */
+  private static int number = 100000;
+
+  /**
+   * Creates a new bank account.
+   * @return A new bank account.
+   */
+	public synchronized Account createAccount() {
+    return new Account(Bank.number++, 0);
+  }
+
+  /**
+   * Gets the current balance of a bank account.
+   * @param account The bank account to get the balance.
+   * @return The current balance of the bank account.
+   * @throws IllegalArgumentException
+   */
+	public long getBalance(Account account) throws IllegalArgumentException {
+    if (account == null) {
+      throw new IllegalArgumentException();
+    } else {
+      return account.balance;
+    }
+  }
+
+  /**
+   * Deposits an amount into a bank account.
+   * @param account The bank account to deposit the amount into.
+   * @param amount The amount to deposit into the bank account.
+   * @throws IllegalArgumentException
+   * @throws IllegalAccountStateException
+   */
+	public void deposit(Account account, long amount) throws IllegalAccountStateException, IllegalArgumentException {
+    
+    if (account == null || amount < 0) {
+      throw new IllegalArgumentException();
+    }
+
+    if ((this.getBalance(account) + amount) > Account.UPPER_LIMIT) {
+      throw new IllegalAccountStateException();
+    } else {
+      account.balance += amount;
+    }
+  }
+
+  /**
+   * Withdraws an amount from a bank account.
+   * @param account The bank account to withdraw the amount from.
+   * @param amount The amount to withdraw from the bank account.
+   * @throws IllegalArgumentException
+   * @throws IllegalAccountStateException
+   */
+	public void withdraw(Account account, long amount) throws IllegalAccountStateException, IllegalArgumentException {
+
+    if (account == null || amount < 0) {
+      throw new IllegalArgumentException();
+    }
+
+    if ((this.getBalance(account) - amount) < Account.LOWER_LIMIT) {
+      throw new IllegalAccountStateException();
+    } else {
+      account.balance -= amount;
+    }
+  }
+
+  /**
+   * Transfers a amount between two bank accounts.
+   * @param fromAccount The bank account to withdraw from.
+   * @param toAccount The bank account to deposit into.
+   * @param amount The amount to transfer between the two bank accounts.
+   * @throws IllegalArgumentException
+   * @throws IllegalAccountStateException
+   */
+	public void transfer(Account fromAccount, Account toAccount, long amount) throws IllegalAccountStateException, IllegalArgumentException {
+
+    if (fromAccount == null || toAccount == null || amount < 0) {
+      throw new IllegalArgumentException();
+    }
+
+    Account a, b;
+    
+    // it is important to lock the accounts always in the same order.
+    // the bank account number is used to sort the bank accounts.
+    if (fromAccount.number > toAccount.number) {
+      a = fromAccount;
+      b = toAccount;
+    } else {
+      a = toAccount;
+      b = fromAccount;
+    }
+
+    // lock the two bank accounts to transfer the amount between them.
+    // a different thread should not be able to do changes while the transfer is running. 
+    synchronized(a) {
+      synchronized(b) {
+        if ((this.getBalance(fromAccount) - amount) < Account.LOWER_LIMIT) {
+          throw new IllegalAccountStateException();
+        }
+        if ((this.getBalance(toAccount) + amount) > Account.UPPER_LIMIT) {
+          throw new IllegalAccountStateException();
+        }
+        this.deposit(fromAccount, amount);
+        this.withdraw(toAccount, amount);
+      }
+    }
+  }
+}

VL03-02-01/src/main/java/de/dhbw/parprog/Example.java

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+package de.dhbw.parprog;
+
+/**
+ * Class which represents an example / demo.
+ */
+public class Example {
+  public static void main(String[] args) {
+
+    // initialize the bank and two bank accounts with initial balance.
+    Bank bank = new Bank();
+    Account a = bank.createAccount();
+    Account b = bank.createAccount();
+    bank.deposit(a, 10000);
+    bank.deposit(b, 10000);
+
+    // output the balance of the bank accounts before running some transfers.
+    System.out.println("Account A=" + a.number + ", Account B=" + b.number);
+    System.out.println("Start Balance: A=" + bank.getBalance(a) + ", B=" + bank.getBalance(b));
+
+    // create and start two threads transfering an amount between the two bank accounts.
+    Thread t1 = new Thread(new Transfer(bank, a, b, 10, 1000));
+    Thread t2 = new Thread(new Transfer(bank, b, a, 10, 1000));
+    t1.start();
+    t2.start();
+
+    // wait until the threads are finished.
+    try {
+      t1.join();
+      t2.join();
+    } catch (InterruptedException e) {
+      e.printStackTrace();
+    }
+
+    // output the balance of the bank accounts after finishing the transfers.
+    System.out.println("End Balance: A=" + bank.getBalance(a) + ", B=" + bank.getBalance(b));
+  }
+}

VL03-02-01/src/main/java/de/dhbw/parprog/IllegalAccountStateException.java

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+package de.dhbw.parprog;
+
+public class IllegalAccountStateException extends RuntimeException {
+  
+}

VL03-02-01/src/main/java/de/dhbw/parprog/Transfer.java

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+package de.dhbw.parprog;
+
+/**
+ * Class which represents a transfer between two bank accounts.
+ */
+public class Transfer implements Runnable {
+
+  /**
+   * The bank of the two bank accounts.
+   */
+  Bank bank;
+
+  /**
+   * The bank account to transfer from.
+   */
+  Account fromAccount;
+
+  /**
+   * The bank account to transfer into.
+   */
+  Account toAccount;
+
+  /**
+   * The amount to transfer between the two bank accounts.
+   */
+  long amount;
+
+  /**
+   * The number of transfers between the two bank accounts.
+   */
+  int count;
+
+  /**
+   * Constructor to create a new transfer between two bank accounts.
+   * @param bank The bank of the bank accounts.
+   * @param fromAccount The bank account to transfer from.
+   * @param toAccount The bank account to transfer into.
+   * @param amount The amount to transfer between the two bank accounts.
+   * @param count The number of transfers between the two bank acocunts.
+   */
+  Transfer(Bank bank, Account fromAccount, Account toAccount, long amount, int count) {
+    this.bank = bank;
+    this.fromAccount = fromAccount;
+    this.toAccount = toAccount;
+    this.amount = amount;
+    this.count = count;
+  }
+
+  /**
+   * The method to do the multiple transfers with a given amount.
+   */
+  public void run() {
+    for (int i = 0; i < this.count; i++) {
+      this.bank.transfer(this.fromAccount, this.toAccount, this.amount);
+    }
+  }
+}

VL03-02-01/src/test/java/de/dhbw/parprog/AccountStateTests.java

@@ -0,0 +1,55 @@
+package de.dhbw.parprog;
+
+import static org.fest.assertions.Assertions.assertThat;
+
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+
+@RunWith(JUnit4.class)
+public class AccountStateTests {
+    Bank bank;
+
+    @Rule
+    public ExpectedException thrown = ExpectedException.none();
+
+    @Before
+    public void setupTest() {
+        bank = new Bank();
+    }
+
+    @Test
+    public void newAccountHasNoCredits() {
+        Account a = bank.createAccount();
+        assertThat(bank.getBalance(a)).isEqualTo(0);
+    }
+
+    @Test
+    public void canDepositAndWithdraw() throws IllegalAccountStateException {
+        Account a = bank.createAccount();
+        bank.deposit(a, 10);
+        bank.withdraw(a, 5);
+    }
+
+    @Test
+    public void cantDepositMoreThanMaximum() throws IllegalAccountStateException {
+        Account a = bank.createAccount();
+        bank.deposit(a, Account.UPPER_LIMIT);
+        thrown.expect(IllegalAccountStateException.class);
+        bank.deposit(a, 1);
+        Assert.fail("Should have caused an exception");
+    }
+
+    @Test
+    public void cantWithdrawBelowMinimum() throws IllegalAccountStateException {
+        Account a = bank.createAccount();
+        thrown.expect(IllegalAccountStateException.class);
+        bank.withdraw(a, 1);
+        Assert.fail("Should have caused an exception");
+    }
+}