mirror of https://github.com/bvn13/jmonad.git
Try Monad in Java
parent
1a8068d6ba
commit
8b651812de
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@ -0,0 +1,16 @@
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plugins {
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id 'java'
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}
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group 'com.bvn13'
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version '1.0-SNAPSHOT'
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sourceCompatibility = 1.8
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repositories {
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mavenCentral()
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}
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dependencies {
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testCompile group: 'junit', name: 'junit', version: '4.12'
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}
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#!/usr/bin/env sh
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##############################################################################
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##
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## Gradle start up script for UN*X
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##
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##############################################################################
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# Attempt to set APP_HOME
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# Resolve links: $0 may be a link
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PRG="$0"
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# Need this for relative symlinks.
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while [ -h "$PRG" ] ; do
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ls=`ls -ld "$PRG"`
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link=`expr "$ls" : '.*-> \(.*\)$'`
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if expr "$link" : '/.*' > /dev/null; then
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PRG="$link"
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else
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PRG=`dirname "$PRG"`"/$link"
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fi
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done
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SAVED="`pwd`"
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cd "`dirname \"$PRG\"`/" >/dev/null
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APP_HOME="`pwd -P`"
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cd "$SAVED" >/dev/null
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APP_NAME="Gradle"
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APP_BASE_NAME=`basename "$0"`
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# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
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DEFAULT_JVM_OPTS=""
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# Use the maximum available, or set MAX_FD != -1 to use that value.
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MAX_FD="maximum"
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warn () {
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echo "$*"
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}
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die () {
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echo
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echo "$*"
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echo
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exit 1
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}
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# OS specific support (must be 'true' or 'false').
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cygwin=false
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msys=false
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darwin=false
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nonstop=false
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case "`uname`" in
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CYGWIN* )
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cygwin=true
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;;
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Darwin* )
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darwin=true
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;;
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MINGW* )
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msys=true
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;;
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NONSTOP* )
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nonstop=true
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;;
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esac
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CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
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# Determine the Java command to use to start the JVM.
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if [ -n "$JAVA_HOME" ] ; then
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if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
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# IBM's JDK on AIX uses strange locations for the executables
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JAVACMD="$JAVA_HOME/jre/sh/java"
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else
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JAVACMD="$JAVA_HOME/bin/java"
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fi
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if [ ! -x "$JAVACMD" ] ; then
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die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
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Please set the JAVA_HOME variable in your environment to match the
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location of your Java installation."
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fi
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else
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JAVACMD="java"
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which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
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Please set the JAVA_HOME variable in your environment to match the
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location of your Java installation."
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fi
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# Increase the maximum file descriptors if we can.
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if [ "$cygwin" = "false" -a "$darwin" = "false" -a "$nonstop" = "false" ] ; then
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MAX_FD_LIMIT=`ulimit -H -n`
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if [ $? -eq 0 ] ; then
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if [ "$MAX_FD" = "maximum" -o "$MAX_FD" = "max" ] ; then
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MAX_FD="$MAX_FD_LIMIT"
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fi
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ulimit -n $MAX_FD
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if [ $? -ne 0 ] ; then
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warn "Could not set maximum file descriptor limit: $MAX_FD"
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fi
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else
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warn "Could not query maximum file descriptor limit: $MAX_FD_LIMIT"
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fi
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fi
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# For Darwin, add options to specify how the application appears in the dock
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if $darwin; then
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GRADLE_OPTS="$GRADLE_OPTS \"-Xdock:name=$APP_NAME\" \"-Xdock:icon=$APP_HOME/media/gradle.icns\""
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fi
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# For Cygwin, switch paths to Windows format before running java
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if $cygwin ; then
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APP_HOME=`cygpath --path --mixed "$APP_HOME"`
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CLASSPATH=`cygpath --path --mixed "$CLASSPATH"`
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JAVACMD=`cygpath --unix "$JAVACMD"`
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# We build the pattern for arguments to be converted via cygpath
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ROOTDIRSRAW=`find -L / -maxdepth 1 -mindepth 1 -type d 2>/dev/null`
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SEP=""
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for dir in $ROOTDIRSRAW ; do
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ROOTDIRS="$ROOTDIRS$SEP$dir"
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SEP="|"
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done
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OURCYGPATTERN="(^($ROOTDIRS))"
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# Add a user-defined pattern to the cygpath arguments
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if [ "$GRADLE_CYGPATTERN" != "" ] ; then
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OURCYGPATTERN="$OURCYGPATTERN|($GRADLE_CYGPATTERN)"
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fi
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# Now convert the arguments - kludge to limit ourselves to /bin/sh
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i=0
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for arg in "$@" ; do
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CHECK=`echo "$arg"|egrep -c "$OURCYGPATTERN" -`
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CHECK2=`echo "$arg"|egrep -c "^-"` ### Determine if an option
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if [ $CHECK -ne 0 ] && [ $CHECK2 -eq 0 ] ; then ### Added a condition
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eval `echo args$i`=`cygpath --path --ignore --mixed "$arg"`
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else
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eval `echo args$i`="\"$arg\""
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fi
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i=$((i+1))
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done
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case $i in
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(0) set -- ;;
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(1) set -- "$args0" ;;
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(2) set -- "$args0" "$args1" ;;
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(3) set -- "$args0" "$args1" "$args2" ;;
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(4) set -- "$args0" "$args1" "$args2" "$args3" ;;
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(5) set -- "$args0" "$args1" "$args2" "$args3" "$args4" ;;
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(6) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" ;;
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(7) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" ;;
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(8) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" ;;
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(9) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" "$args8" ;;
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esac
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fi
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# Escape application args
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save () {
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for i do printf %s\\n "$i" | sed "s/'/'\\\\''/g;1s/^/'/;\$s/\$/' \\\\/" ; done
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echo " "
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}
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APP_ARGS=$(save "$@")
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# Collect all arguments for the java command, following the shell quoting and substitution rules
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eval set -- $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS "\"-Dorg.gradle.appname=$APP_BASE_NAME\"" -classpath "\"$CLASSPATH\"" org.gradle.wrapper.GradleWrapperMain "$APP_ARGS"
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# by default we should be in the correct project dir, but when run from Finder on Mac, the cwd is wrong
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if [ "$(uname)" = "Darwin" ] && [ "$HOME" = "$PWD" ]; then
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cd "$(dirname "$0")"
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fi
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exec "$JAVACMD" "$@"
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@ -0,0 +1,84 @@
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@if "%DEBUG%" == "" @echo off
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@rem ##########################################################################
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@rem
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@rem Gradle startup script for Windows
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@rem
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@rem ##########################################################################
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@rem Set local scope for the variables with windows NT shell
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if "%OS%"=="Windows_NT" setlocal
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set DIRNAME=%~dp0
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if "%DIRNAME%" == "" set DIRNAME=.
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set APP_BASE_NAME=%~n0
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set APP_HOME=%DIRNAME%
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@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
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set DEFAULT_JVM_OPTS=
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@rem Find java.exe
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if defined JAVA_HOME goto findJavaFromJavaHome
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set JAVA_EXE=java.exe
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%JAVA_EXE% -version >NUL 2>&1
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if "%ERRORLEVEL%" == "0" goto init
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echo.
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echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
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echo.
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echo Please set the JAVA_HOME variable in your environment to match the
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echo location of your Java installation.
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goto fail
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:findJavaFromJavaHome
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set JAVA_HOME=%JAVA_HOME:"=%
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set JAVA_EXE=%JAVA_HOME%/bin/java.exe
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if exist "%JAVA_EXE%" goto init
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echo.
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echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
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echo.
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echo Please set the JAVA_HOME variable in your environment to match the
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echo location of your Java installation.
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goto fail
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:init
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@rem Get command-line arguments, handling Windows variants
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if not "%OS%" == "Windows_NT" goto win9xME_args
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:win9xME_args
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@rem Slurp the command line arguments.
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set CMD_LINE_ARGS=
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set _SKIP=2
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:win9xME_args_slurp
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if "x%~1" == "x" goto execute
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set CMD_LINE_ARGS=%*
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:execute
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@rem Setup the command line
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set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
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@rem Execute Gradle
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"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %CMD_LINE_ARGS%
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:end
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@rem End local scope for the variables with windows NT shell
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if "%ERRORLEVEL%"=="0" goto mainEnd
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:fail
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rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
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rem the _cmd.exe /c_ return code!
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if not "" == "%GRADLE_EXIT_CONSOLE%" exit 1
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exit /b 1
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:mainEnd
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if "%OS%"=="Windows_NT" endlocal
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:omega
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@ -0,0 +1,2 @@
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rootProject.name = 'jmonad'
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@ -0,0 +1,61 @@
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package com.bvn13.jmonad;
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import java.util.Objects;
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import java.util.Optional;
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import java.util.function.Function;
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/**
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* Created by bvn13 on 10.06.2019.
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*/
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public class Failure<T> extends Try<T> {
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private final Throwable e;
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Failure(Throwable e) {
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this.e = e;
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}
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@Override
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public T get() throws Throwable {
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throw e;
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}
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@Override
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public T orElse(T value) {
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return value;
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}
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@Override
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public <U> Try<U> flatMap(Function<? super T, ? extends U> f) {
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Objects.requireNonNull(f);
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return Try.failure(e);
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}
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@Override
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public Try<T> filter(Function<? super T, ? extends Boolean> f) {
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Objects.requireNonNull(f);
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return Try.failure(e);
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}
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@Override
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public Try<T> map(Function<? super T, ? extends T> f) {
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Objects.requireNonNull(f);
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return Try.failure(e);
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}
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@Override
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public T orElseThrow(Throwable e) throws Throwable {
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Objects.requireNonNull(e);
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throw e;
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}
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@Override
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public Optional<T> toOptional() {
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return Optional.empty();
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}
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@Override
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public boolean isSuccess() {
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return false;
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}
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}
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package com.bvn13.jmonad;
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import com.bvn13.jmonad.exceptions.ValueNotFoundException;
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import java.util.Objects;
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import java.util.Optional;
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import java.util.function.Function;
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/**
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* Created by bvn13 on 10.06.2019.
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*/
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public class Success<T> extends Try<T> {
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private final T value;
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Success(T value) {
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this.value = value;
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}
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@Override
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public T get() {
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return value;
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}
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@Override
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public T orElse(T value) {
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return this.value;
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}
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@Override
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public <U> Try<U> flatMap(Function<? super T, ? extends U> f) {
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Objects.requireNonNull(f);
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return Try.successful(f.apply(value));
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}
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@Override
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public Try<T> filter(Function<? super T, ? extends Boolean> f) {
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Objects.requireNonNull(f);
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if (f.apply(value)) {
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return Try.successful(value);
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} else {
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return Try.failure(new ValueNotFoundException("not found"));
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}
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}
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@Override
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public Try<T> map(Function<? super T, ? extends T> f) {
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Objects.requireNonNull(f);
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return Try.successful(f.apply(value));
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}
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@Override
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public T orElseThrow(Throwable e) throws Throwable {
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Objects.requireNonNull(e);
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return value;
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}
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@Override
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public Optional<T> toOptional() {
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return Optional.ofNullable(value);
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}
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@Override
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public boolean isSuccess() {
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return true;
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}
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}
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@ -0,0 +1,49 @@
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package com.bvn13.jmonad;
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import java.util.Objects;
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import java.util.Optional;
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import java.util.function.Function;
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import java.util.function.Supplier;
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/**
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* Full implementation of Try monad
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* @see <a href="https://medium.com/swlh/write-a-monad-in-java-seriously-50a9047c9839">Source article</a>
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*
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* Created by bvn13 on 10.06.2019.
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*/
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public abstract class Try<T> {
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public static <U> Try<U> ofThrowable(Supplier<U> f) {
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Objects.requireNonNull(f);
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try {
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return Try.successful(f.get());
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} catch (Throwable e) {
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return Try.failure(e);
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}
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}
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public static <U> Success<U> successful(U u) {
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return new Success<>(u);
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}
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public static <U> Failure<U> failure(Throwable e) {
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return new Failure<>(e);
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}
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public abstract T get() throws Throwable;
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public abstract T orElse(T value);
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public abstract <U> Try<U> flatMap(Function<? super T, ? extends U> f);
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public abstract Try<T> filter(Function<? super T, ? extends Boolean> f);
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public abstract Try<T> map(Function<? super T, ? extends T> f);
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public abstract T orElseThrow(Throwable e) throws Throwable;
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public abstract Optional<T> toOptional();
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public abstract boolean isSuccess();
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}
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@ -0,0 +1,26 @@
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package com.bvn13.jmonad.exceptions;
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/**
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* Created by bvn13 on 10.06.2019.
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*/
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public class ValueNotFoundException extends RuntimeException {
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public ValueNotFoundException() {
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super();
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}
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public ValueNotFoundException(String message) {
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super(message);
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}
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public ValueNotFoundException(String message, Throwable cause) {
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super(message, cause);
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}
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public ValueNotFoundException(Throwable cause) {
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super(cause);
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}
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protected ValueNotFoundException(String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace) {
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super(message, cause, enableSuppression, writableStackTrace);
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}
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}
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@ -0,0 +1,92 @@
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package com.bvn13.jmonad;
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import org.junit.Test;
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import static org.junit.Assert.*;
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/**
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* Created by bvn13 on 10.06.2019.
|
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*/
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public class TryTest {
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@Test
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public void testTryFirstProbe() throws Throwable {
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Try.ofThrowable(() -> String.valueOf(10))
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.get();
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}
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@Test
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public void testTryInteger() throws Throwable {
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Try<Integer> value = Try.ofThrowable(() -> Integer.valueOf("1"));
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assertEquals(Integer.valueOf(1), value.get());
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}
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@Test
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public void testTryIntegerAdd() throws Throwable {
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String value = Try.ofThrowable(() -> Integer.valueOf("1"))
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.flatMap(v -> String.format("%d", v))
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.get();
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assertEquals("1", value);
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}
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||||
@Test
|
||||
public void testFailureWithDefault() {
|
||||
int value = Try.ofThrowable(() -> Integer.valueOf("T"))
|
||||
.orElse(5);
|
||||
assertEquals(5, value);
|
||||
}
|
||||
|
||||
@Test
|
||||
public void testFilter() throws Throwable {
|
||||
int value = Try.ofThrowable(() -> Integer.valueOf("1"))
|
||||
.filter(i -> i > 0)
|
||||
.get();
|
||||
assertEquals(1, value);
|
||||
int notValue = Try.ofThrowable(() -> Integer.valueOf("1"))
|
||||
.filter(i -> i < 0)
|
||||
.orElse(10);
|
||||
assertEquals(10, notValue);
|
||||
}
|
||||
|
||||
@Test
|
||||
public void testMap() throws Throwable {
|
||||
int value = Try.ofThrowable(() -> Integer.valueOf("1"))
|
||||
.map(i -> i + 20)
|
||||
.get();
|
||||
assertEquals(21, value);
|
||||
}
|
||||
|
||||
@Test
|
||||
public void testOrElseThrow() throws Throwable {
|
||||
Throwable t = null;
|
||||
|
||||
try {
|
||||
int value = Try.ofThrowable(() -> Integer.valueOf("1"))
|
||||
.filter(v -> v < 0)
|
||||
.orElseThrow(new IllegalArgumentException("!!!"));
|
||||
} catch (Throwable e) {
|
||||
t = e;
|
||||
}
|
||||
|
||||
assertTrue(t instanceof IllegalArgumentException);
|
||||
}
|
||||
|
||||
@Test
|
||||
public void testToOptional() {
|
||||
int value = Try.ofThrowable(() -> Integer.valueOf("1"))
|
||||
.toOptional().orElse(2);
|
||||
assertEquals(1, value);
|
||||
int notValue = Try.ofThrowable(() -> Integer.valueOf(""))
|
||||
.toOptional().orElse(2);
|
||||
assertEquals(2, notValue);
|
||||
}
|
||||
|
||||
@Test
|
||||
public void testIsSuccess() {
|
||||
boolean success = Try.ofThrowable(() -> Integer.valueOf("1")).isSuccess();
|
||||
assertTrue(success);
|
||||
boolean failure = Try.ofThrowable(() -> Integer.valueOf("")).isSuccess();
|
||||
assertFalse(failure);
|
||||
}
|
||||
|
||||
}
|
Loading…
Reference in New Issue