将JDK1.5 ThreadLocal代码移植到JDK1.4

Question

I have below piece code which runs on JDK5

private static ThreadLocal<String> messages = new ThreadLocal<String>();
private static ThreadLocal<Boolean> dontIntercept = new ThreadLocal<Boolean>() {
    @Override
    protected Boolean initialValue() {
        return Boolean.FALSE;
        }
};

I wish to run it on JDK1.4. Please advice what changes will be required

Answer 1

You will have to get rid of the generics and then cast the values appropriately when using the get and put methods. You'll also need to ensure that the boolean ThreadLocal is initialised correctly where it is used in the code.

Answer 2

• Remove generics.
• Remove covariant return.
• Remove @Override annotation.

So

private static final ThreadLocal messages = new ThreadLocal();
private static final ThreadLocal dontIntercept = new ThreadLocal() {
    protected Object initialValue() {
        return Boolean.FALSE;
    }
};

When using

• Cast value back to Boolean .
• Unbox with .booleanValue() .
• Box with Boolean.valueOf .

Answer 3

If the program is correctly written to Java 1.4 behaviour, but uses Java 1.5+ notation, an approach we have used several times is to use Retroweaver to convert the compiled Java 1.5 byte code to Java 1.4 byte code.

http://retroweaver.sourceforge.net/

Others exist, but this is the one we have found to work the best.

Answer 4

You could always download the source code from sun and have a look at the ThreadLocal class.

Or use this link