"javac -source 10 -target 10" - Lower Java Version
How to lower the Java version in the bytecode? I want to generate class files for an older Java environment.
✍: FYIcenter
If you want generate class files for an older Java environment,
you need to use "-source x" and "-target x" options
in the "javac" command to compile the Java source code.
1. Check the default version of Java compiler:
> javac -version javac 15
2. Compile HelloWorldFrame.java used in the last tutorial into a bytecode file with the default version:
> javac HelloWorldFrame.java
3. Check the version of the bytecode. Bytecode major version 59 maps to Java 15.
> javap -v HelloWorldFrame.class | grep "major version" major version: 59
4. Compile HelloWorldFrame.java again for Java 10:
> javac -source 10 -target 10 HelloWorldFrame.java warning: [options] system modules path not set in conjunction with -source 10 1 warning
5. Check the version of the bytecode again. Bytecode major version 54 maps to Java 10.
> javap -v HelloWorldFrame.class | grep major major version: 54
This bytecode can be executed in Java 10 environment.
⇒ "javap jar:file:" - Specify Bytecode in JAR
2021-09-09, 448👍, 0💬
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