rust调用java实现方法

（1）Cargo.toml 增加：

j4rs = "0.18.0"

(2)java源码：

public class HelloWorld {
    public static String sayHello(String name) {
			return "Hello "+name;
    }
}

编译：
javac HelloWorld.java

生成HelloWorld.class，设class所在目录是/tmp

(3)rust代码调用java:

main.rs:

use j4rs::{ClasspathEntry, Instance, InvocationArg, Jvm, JvmBuilder};
fn main() {
    let entry = ClasspathEntry::new("/tmp");
    let jvm: Jvm = JvmBuilder::new().classpath_entry(entry).build().unwrap();
	 let parameter= "hello";
	 let result_instance= jvm
        .invoke_static(
            "HelloWorld", // The Java class to invoke
            "sayHello",   // The static method of the Java class to invoke
            &[InvocationArg::try_from(parameter).unwrap()],
        )
        .unwrap();

    let result: String = jvm.to_rust(result_instance).unwrap();
    print!("{}", result);
}