var name = "mcc";
var version = "1.0";
var java = System.getProperty("java.home");
var jvmArgs = "-XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=16M -XX:-UseAdaptiveSizePolicy -XX:-OmitStackTraceInFastThrow -Xmn128m -Xmx1792m";
var natives = "C:/Users/Enaium/AppData/Roaming/.minecraft/versions/1.8.9/natives";
var libraries = "C:/Users/Enaium/AppData/Roaming/.minecraft/libraries/com/mojang/netty/1.6/netty-1.6.jar;C:/Users/Enaium/AppData/Roaming/.minecraft/libraries/oshi-project/oshi-core/1.1/oshi-core-1.1.jar;C:/Users/Enaium/AppData/Roaming/.minecraft/libraries/net/java/dev/jna/jna/3.4.0/jna-3.4.0.jar;C:/Users/Enaium/AppData/Roaming/.minecraft/libraries/net/java/dev/jna/platform/3.4.0/platform-3.4.0.jar;C:/Users/Enaium/AppData/Roaming/.minecraft/libraries/com/ibm/icu/icu4j-core-mojang/51.2/icu4j-core-mojang-51.2.jar;C:/Users/Enaium/AppData/Roaming/.minecraft/libraries/net/sf/jopt-simple/jopt-simple/4.6/jopt-simple-4.6.jar;C:/Users/Enaium/AppData/Roaming/.minecraft/libraries/com/paulscode/codecjorbis/20101023/codecjorbis-20101023.jar;C:/Users/Enaium/AppData/Roaming/.minecraft/libraries/com/paulscode/codecwav/20101023/codecwav-20101023.jar;C:/Users/Enaium/AppData/Roaming/.minecraft/libraries/com/paulscode/libraryjavasound/20101123/libraryjavasound-20101123.jar;C:/Users/Enaium/AppData/Roaming/.minecraft/libraries/com/paulscode/librarylwjglopenal/20100824/librarylwjglopenal-20100824.jar;C:/Users/Enaium/AppData/Roaming/.minecraft/libraries/com/paulscode/soundsystem/20120107/soundsystem-20120107.jar;C:/Users/Enaium/AppData/Roaming/.minecraft/libraries/io/netty/netty-all/4.0.23.Final/netty-all-4.0.23.Final.jar;C:/Users/Enaium/AppData/Roaming/.minecraft/libraries/com/google/guava/guava/17.0/guava-17.0.jar;C:/Users/Enaium/AppData/Roaming/.minecraft/libraries/org/apache/commons/commons-lang3/3.3.2/commons-lang3-3.3.2.jar;C:/Users/Enaium/AppData/Roaming/.minecraft/libraries/commons-io/commons-io/2.4/commons-io-2.4.jar;C:/Users/Enaium/AppData/Roaming/.minecraft/libraries/commons-codec/commons-codec/1.9/commons-codec-1.9.jar;C:/Users/Enaium/AppData/Roaming/.minecraft/libraries/net/java/jinput/jinput/2.0.5/jinput-2.0.5.jar;C:/Users/Enaium/AppData/Roaming/.minecraft/libraries/net/java/jutils/jutils/1.0.0/jutils-1.0.0.jar;C:/Users/Enaium/AppData/Roaming/.minecraft/libraries/com/google/code/gson/gson/2.2.4/gson-2.2.4.jar;C:/Users/Enaium/AppData/Roaming/.minecraft/libraries/com/mojang/authlib/1.5.21/authlib-1.5.21.jar;C:/Users/Enaium/AppData/Roaming/.minecraft/libraries/com/mojang/realms/1.7.59/realms-1.7.59.jar;C:/Users/Enaium/AppData/Roaming/.minecraft/libraries/org/apache/commons/commons-compress/1.8.1/commons-compress-1.8.1.jar;C:/Users/Enaium/AppData/Roaming/.minecraft/libraries/org/apache/httpcomponents/httpclient/4.3.3/httpclient-4.3.3.jar;C:/Users/Enaium/AppData/Roaming/.minecraft/libraries/commons-logging/commons-logging/1.1.3/commons-logging-1.1.3.jar;C:/Users/Enaium/AppData/Roaming/.minecraft/libraries/org/apache/httpcomponents/httpcore/4.3.2/httpcore-4.3.2.jar;C:/Users/Enaium/AppData/Roaming/.minecraft/libraries/org/apache/logging/log4j/log4j-api/2.0-beta9/log4j-api-2.0-beta9.jar;C:/Users/Enaium/AppData/Roaming/.minecraft/libraries/org/apache/logging/log4j/log4j-core/2.0-beta9/log4j-core-2.0-beta9.jar;C:/Users/Enaium/AppData/Roaming/.minecraft/libraries/org/lwjgl/lwjgl/lwjgl/2.9.4-nightly-20150209/lwjgl-2.9.4-nightly-20150209.jar;C:/Users/Enaium/AppData/Roaming/.minecraft/libraries/org/lwjgl/lwjgl/lwjgl_util/2.9.4-nightly-20150209/lwjgl_util-2.9.4-nightly-20150209.jar;C:/Users/Enaium/AppData/Roaming/.minecraft/libraries/tv/twitch/twitch/6.5/twitch-6.5.jar;C:/Users/Enaium/AppData/Roaming/.minecraft/versions/1.8.9/1.8.9.jar";
var mainClass = "net.minecraft.client.main.Main";
var username = "Enaium";
var gameVersion = "\" " + name + " " + version + " \"";
var gameDir = "C:/Users/Enaium/AppData/Roaming/.minecraft";
var assetsDir = "C:/Users/Enaium/AppData/Roaming/.minecraft/assets";
var assetIndex = "1.8";
var uuid = "0";
var accessToken = "0";
var text = java + "/bin/java.exe " + jvmArgs + " -Djava.library.path=" + natives + " -Dminecraft.launcher.brand="
        + name + " -Dminecraft.launcher.version=" + version + " -cp " + libraries + " " + mainClass
        + " --username " + username + " --version " + gameVersion +
        " --gameDir " + gameDir + " --assetsDir " + assetsDir + " --assetIndex " + assetIndex
        + " --uuid " + uuid + " --accessToken " + accessToken + " --userProperties {} --userType mojang "
        + "--width 854 --height 480";

把每一个参数都提取出来,放到变量里

try {
    var exec = Runtime.getRuntime().exec(text);
    BufferedReader br = new BufferedReader(new InputStreamReader(exec.getInputStream()));
    String line;
    while ((line = br.readLine()) != null) {
        System.out.println(line);
    }
} catch (IOException e) {
    e.printStackTrace();
}

执行命令,之后输出

在项目目录创建run,修改运行目录到这

image-20210515125706790

启动成功