docs(bindings/java): add basic usage in README

[caicancai]

close #3522

test success

[tisonkun]

I suspect if we should add such an example. But if it's well-written, that can be fine.

[caicancai]

Do you want me to put this example in java test as a basic test

[tisonkun]

Do you want me to put this example in java test as a basic test

No. Our tests have coverage already.

Such an example can either serve in:

• https://github.com/apache/incubator-opendal/blob/main/bindings/java/README.md
• or https://github.com/apache/incubator-opendal/tree/main/examples

[caicancai]

Do you want me to put this example in java test as a basic test

No. Our tests have coverage already.

Such an example can either serve in:

• https://github.com/apache/incubator-opendal/blob/main/bindings/java/README.md
• or https://github.com/apache/incubator-opendal/tree/main/examples

• https://github.com/apache/incubator-opendal/tree/main/examples

Thank you for your reply, on https://github.com/apache/incubator-opendal/tree/main/examples, it seems, are still need some other documents, is needed in my pr supplement or the next pr

[caicancai]

@tisonkun hi, could you please help review this pr if you have time? At present, I plan to simply add an example in the readme