What's the difference between a package and an import? [duplicate]

问题

What's the difference between a package and an import? Please give an example.

Why can't we just use import java.util.*;?
Doesn't it give access to all the others automatically?

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class RegexMatches
{
public static void main( String args[] ){

  // String to be scanned to find the pattern.
  String line = "This order was placed for QT3000! OK?";
  String pattern = "(.*)(\\d+)(.*)";

  // Create a Pattern object
  Pattern r = Pattern.compile(pattern);

  // Now create matcher object.
  Matcher m = r.matcher(line);
  if (m.find( )) {
     System.out.println("Found value: " + m.group(0) );
     System.out.println("Found value: " + m.group(1) );
     System.out.println("Found value: " + m.group(2) );
  } else {
     System.out.println("NO MATCH");
  }
 }
}

回答1:

sentence "import java.util." imports only the classes under the util package. You can use "import java.util.regex." to import Matcher and Pattern classes . A package is a namespace for your classes, it's used to group related classes togheter and for access privilege reasons.

回答2:

Package is used to put all one Module related into one specified Folder for a better understanding ,whereas import is used to import the specific class that we need to run our application/class(Like we use Java.Util...etc).

回答3:

package name is user defined its what you give,

Ex: package test;

import package is used to get already predefined packages in java to be used in your current package

Ex: if you want to use "util" package in your test package,

package test;

java.util.Scanner;

Here util is java predefined package and Scanner is the class present in util package.

回答4:

Package is used to put all our related classes into one specified Folder for a better understanding ,whereas import is used to import(get) the needed or the dependent classes to run our application/class.

来源：https://stackoverflow.com/questions/23580284/whats-the-difference-between-a-package-and-an-import

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