Jack compiler and java 8 make Android apps grabled

Question

When I started to use jack compiler and java 8 to develop an Android app, I found the normal words become garbled like this:

This text should be a Chinese, but it became garbled. And this is my build.gradle:

apply plugin: 'com.android.application'

android {
    compileSdkVersion 24
    buildToolsVersion "24.0.1"
    defaultConfig {
        applicationId "com.li.test"
        minSdkVersion 16
        targetSdkVersion 24
        versionCode 1
        versionName "1.0"

        jackOptions {
            enabled true
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

But when I don't use the jack compiler and java 8, the garbled text returned to normal:

All I have done is deleting the jackOptions and compileOptions in the build.gradle.

My file encoding is UTF-8.

How can I avoid the garbled text when I use jack and java 8 ? Or is this a bug ?