instanceof 的使用<pattern>在 NetBeans 11.3 + OpenJDK 14</pattern>

Question

After OpenJDK update to 14, the instanceof grammar was extended, so now we can use patterns: RelationalExpression instanceof Pattern . More info here . In NetBeans 11.3 I noticed the hint instanceof <pattern> can be used here near this method:

public String getTLSCipherSuite() {
    if (socket instanceof SSLSocket) {
        return ((SSLSocket) socket).getSession().getCipherSuite();
    }
    return null;
}

If I change reference type to pattern, I see NetBeans error:

public String getTLSCipherSuite() {
    if (socket instanceof SSLSocket sslSocket) {//<--- ")" expected
        return sslSocket.getSession().getCipherSuite();
    }
    return null;
}

Perhaps it's NetBeans bug?

Answer 1

This JDK 14 feature can only be used if NetBeans 11.3 itself is running on Java 14 javac, not the nb-javac packaged with NetBeans 11.3. The java compiler's --enable-preview flag must be set also. See https://netbeans.apache.org/download/nb113/index.html for details. Of course, running NetBeans on javac instead of nb-javac means losing the nb-javac advantages. See the links in https://blogs.apache.org/netbeans/entry/what-s-nb-javac-in for a discussion of the trade-offs. The instanceof syntax is still listed as a preview feature in JDK 15, so there is no guarantee it won't change in future Java versions.