NoClassDefFoundError

build.gradle

plugins {
    id "java"
    id "application"
}

configurations {
    compileClasspath.resolutionStrategy.activateDependencyLocking()
    runtimeClasspath.resolutionStrategy.activateDependencyLocking()
}

repositories {
    mavenCentral()
}

java {
    toolchain {
        languageVersion = JavaLanguageVersion.of(8)
    }
}

tasks.withType(JavaCompile) {
    options.compilerArgs << "-Xlint:deprecation" << "-Xlint:unchecked"
    options.encoding = "UTF-8"
}

sourceSets {
    main {
        java {
            srcDir '.'
        }
    }
}

dependencies {
    compileOnly "org.msgpack:msgpack-core:0.8.24"
}

application {
    mainClass = "Main"
}

Main.java

public class Main {
    public static void main(final String[] args) {
        System.out.println("#1");
        Sub.safe();
        Sub.unsafe1(null);
        Sub.unsafe2(null);
        Sub.unsafe3(null);
        Sub.unsafe4(null);
        System.out.println("#2");
    }
}

Sub.java

import org.msgpack.value.Value;

public class Sub {
    public static void safe() {
        System.out.println("Safe");
    }

    public static void unsafe1(final Value value) {
        System.out.println("Unsafe1");
    }

    public static void unsafe2(final Value value) {
        System.out.println("Unsafe2");
        if (value == null) {
            System.out.println("null");
        } else {
            System.out.println(value.toString());
        }
    }

    public static void unsafe3(final Value value) {
        System.out.println("Unsafe3");
        try {
            System.out.println(value.toJson());
        } catch (final Throwable ex) {
            ex.printStackTrace(System.out);
        }
    }

    public static void unsafe4(final Value value) {
        System.out.println("Unsafe4");
        try {
            System.out.println(value.toString());
        } catch (final Throwable ex) {
            ex.printStackTrace(System.out);
        }
    }
}

$ ./gradlew run
> Task :run
Picked up JAVA_TOOL_OPTIONS: -Duser.language=en
#1
Safe
Unsafe1
Unsafe2
null
Unsafe3
java.lang.NoClassDefFoundError: org/msgpack/value/Value
        at Sub.unsafe3(Sub.java:24)
        at Main.main(Main.java:7)
Caused by: java.lang.ClassNotFoundException: org.msgpack.value.Value
        at java.net.URLClassLoader.findClass(URLClassLoader.java:382)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
        ... 2 more
Unsafe4
java.lang.NullPointerException
        at Sub.unsafe4(Sub.java:33)
        at Main.main(Main.java:8)
#2

BUILD SUCCESSFUL in 673ms
2 actionable tasks: 1 executed, 1 up-to-date