Java – jdk8 with – source 1.7 [default method]

I have the following classes

public class zoneddatetimeToInstant {

    public static void main(final String[] args)
        throws NoSuchMethodException {

        assert Chronozoneddatetime.class.isAssignableFrom(zoneddatetime.class);
        final Method toInstant
            = Chronozoneddatetime.class.getmethod("toInstant");

        final zoneddatetime Now = zoneddatetime.Now();
        final Instant instant = Now.toInstant();

        System.out.println(instant);
    }
}

It just compiles fine

& javac zoneddatetimeToInstant.java

And it failed with - source 1.7

& javac -source 1.7 zoneddatetimeToInstant.java
zoneddatetimeToInstant.java:10: error: cannot find symbol
    final Instant instant = Now.toInstant();
                               ^
  symbol:   method toInstant()
  location: variable Now of type zoneddatetime
1 error
1 warning

Is this normal? It seems that javac can't remove the JDK class of - source other than 1.8

According to javac, javac still supports various - source version options, just like previous versions

supplement

I already know that the JSR 310: date and time API is only available in Java 8 What does it have to do with javac?

$cat Java8.java
public class Java8 {
    public void print(java.io.PrintStream out) {
        out.printf("hello world\n");
    }
}
$javac Java8.java
$cat Java7.java
public class Java7 {
    public static void main(final String[] args) {
        new Java8().print(System.out);
    }
}
$javac -source 1.7 -target 1.7 Java7.java
warning: [options] bootstrap class path not set in conjunction with -source 1.7
1 warning
$java Java7
hello world

conclusion

As @ Eng. Fouad said The problem is that this method is the default method defined in the interface Javac seems to grasp this point

$cat Java8i.java
public interface Java8i {
    default void print(java.io.PrintStream out) {
        out.printf("hello world\n");
    }
}
$javac Java8i.java
$cat Java8c.java
public class Java8c implements Java8i {
}
$javac Java8c.java
$cat Java7i.java
public class Java7i {
    public static void main(final String[] args) {
        new Java8c().print(System.out);
    }
}
$javac -source 1.7 -target 1.7 Java7i.java
warning: [options] bootstrap class path not set in conjunction with -source 1.7
Java7i.java:3: error: cannot find symbol
    new Java8c().print(System.out);
                ^
  symbol:   method print(PrintStream)
  location: class Java8c
1 error
1 warning

Javac should tell me more helpfully

Solution

This is a new time / date API introduced in Java 8 This is why it cannot be compiled in Java 7

Toinstant() is a default method, while - source 1.7 does not support the default method (a new feature of Java 8)