Improve: Java APIを色々改善 #2257

Job	Run time
actionlint	20s
shellcheck	20s
rust-lint	12m 38s
validate-cargo-lock	31s
build-unix-cpp-example (macos-latest, osx-x64-cpu-cpp-shared)	3m 2s
c-header	46s
build-unix-cpp-example (ubuntu-latest, linux-x64-cpu-cpp-shared)	1m 39s
rust-integration-test-strategy-matrix	1s
rust-unit-test	10m 29s
build-and-test-java-api (windows-latest)	6m 3s
build-and-test-java-api (macos-latest)	3m 29s
build-and-test-python-api (windows-latest)	9m 10s
build-windows-cpp-example	7m 14s
build-and-test-java-api (ubuntu-latest)	4m 45s
build-and-test-python-api (macos-latest)	7m 23s
build-and-test-python-api (ubuntu-latest)	2m 30s
rust-integration-test (windows-2019, directml)	8m 46s
rust-integration-test (macos-11)	8m 38s
rust-integration-test (ubuntu-20.04)	4m 1s
	1h 31m 45s

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