[1.7.10] compileJava failed with 1 error and 1 warning [Unsolved]

Hello,

I want to build my mod, and in the process it fails the

compileJava

task. This is the log:

C:\Users\Lars\Desktop\Modding-Development\MineTech>gradlew build
****************************
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MCP Data version : unknown
****************************
:apiJar UP-TO-DATE
:compileApiJava UP-TO-DATE
:processApiResources UP-TO-DATE
:apiClasses UP-TO-DATE
:sourceMainJava UP-TO-DATE
:compileJava
warning: [options] bootstrap class path not set in conjunction with -source 1.6
C:\Users\Lars\Desktop\Modding-Development\MineTech\build\sources\java\larsg310\m
ods\minetech\multiblock\Multiblocks.java:12: error: cannot find symbol
        STEEL_FURNACE = new MultiblockSteelFurnace();
                            ^
  symbol:   class MultiblockSteelFurnace
  location: class Multiblocks
Note: Some input files use unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.
1 error
1 warning
:compileJava FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':compileJava'.
> Compilation failed; see the compiler error output for details.

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug
option to get more log output.

BUILD FAILED

Total time: 48.43 secs

However, Eclipse doesn't show any compile errors and I can run my mod fine in Eclipse. Here is my

build.gradle

:

buildscript {
    repositories {
        mavenCentral()
        maven {
            name = "forge"
            url = "http://files.minecraftforge.net/maven"
        }
        maven {
            name = "sonatype"
            url = "https://oss.sonatype.org/content/repositories/snapshots/"
        }
    }
    dependencies {
        classpath 'net.minecraftforge.gradle:ForgeGradle:1.2-SNAPSHOT'
    }
}

apply plugin: 'forge'

version = "v0.01-1.7.10"
group= "larsg310.mods.minetech"
archivesBaseName = "MineTech"

minecraft {
    version = "1.7.10-10.13.4.1481-1.7.10"
    runDir = "eclipse"
}

dependencies {

}

task deobfJar(type: Jar) {
    from sourceSets.main.output
    classifier = 'deobf'
}

task sourceJar(type: Jar) {
    from sourceSets.main.allSource
    classifier = 'sources'
}

task apiJar(type: Jar) {
    from(sourceSets.main.allSource) {
        include 'larsg310/mods/minetech/api/**'
    }
    classifier = 'api'
}

tasks.build.dependsOn('sourceJar', 'deobfJar', 'apiJar')

processResources
{
    inputs.property "version", project.version
    inputs.property "mcversion", project.minecraft.version
    from(sourceSets.main.resources.srcDirs) {
        include 'mcmod.info'
                
        expand 'version':project.version, 'mcversion':project.minecraft.version
    }
        
    from(sourceSets.main.resources.srcDirs) {
        exclude 'mcmod.info'
    }
}

The console log is refering to this class:

package larsg310.mods.minetech.multiblock;

import larsg310.mods.minetech.api.multiblock.Multiblock;
import larsg310.mods.minetech.api.multiblock.MultiblockRegistry;

public class Multiblocks
{
    public static Multiblock STEEL_FURNACE;
    
    public static void registerMultiblocks()
    {
        STEEL_FURNACE = new MultiblockSteelFurnace(); //This is the line the console is referring to
        MultiblockRegistry.registerMultiblock(STEEL_FURNACE);
    }
}

I don't have a constructor in the MultiblockSteelFurnace class, so it uses the default constructor.

Does anyone know what is causing the issue? I must be missing something very obvious.

add

sourceCompatibility = 1.7

targetCompatibility = 1.7

after 'apply plugin'