CSC300: Python to Java: Import [28/40] Previous pageContentsNext page

PythonJava
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print ("Hello")
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package algs11;
import stdlib.*;
public class Hello {
  public static void main (String[] args) {
    StdOut.println ("Hello");
  }
}

System.out and System.in refer to objects.

I don't want to talk about objects yet, so we will use the version about, which replaces System.out with StdOut.

StdOut is a class in the stdlib package.

System is a class in the java.lang package.

All of the classes in java.lang are imported implicitly into every java program. All other classes must be imported explicitly.

The statement import stdlib.* makes the classes declared in stdlib visible in our program.

Instead of importing every class from a package, you can also import a single class.

Unnecessary imports will generate a warning.

If your code has a compiler error, it will not run.

If your code has a warning, you can run it. But you should fix the warning.

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