Example failed

[zhoushuntong]

E:\work\polkadot-java\polkaj\examples\balance\src\main\java\Balance.java:1: 错误: 无法访问PolkadotHttpApi
import io.emeraldpay.polkaj.apihttp.PolkadotHttpApi;
^
错误的类文件: C:\Users\zhoushuntong.m2\repository\io\emeraldpay\polkaj\polkaj-api-http\0.4.0-SNAPSHOT\polkaj-api-http-0.4.0-SNAPSHOT.jar(io/emeraldpay/polkaj/apihttp/PolkadotHttpApi.class)
类文件具有错误的版本 55.0, 应为 52.0
请删除该文件或确保该文件位于正确的类路径子目录中。

FAILURE: Build failed with an exception.

[crow123]

update jdk8 to jdk11

[paulvi]

Indeed root build.gradle says

targetCompatibility = '11'
sourceCompatibility = '11'

So JDK 11+ is required