Function Java_dev_yog_NativeBridge_nativeOnItemInsert 

#[unsafe(no_mangle)]
pub extern "system" fn Java_dev_yog_NativeBridge_nativeOnItemInsert<'l>(
    env: JNIEnv<'l>,
    _class: JClass<'l>,
    block: JString<'l>,
    x: jint,
    y: jint,
    z: jint,
    dimension: JString<'l>,
    item_id: JString<'l>,
    count: jint,
    nbt: JString<'l>,
    simulate: jboolean,
) -> jboolean

A hopper or dropper offers an item to a block that accepts items: simulate asks whether it would take it (Pre), else it takes it (Post).