Import package
To import a specific package into the current file, use import statement.
/**
* If you do not use a package statement ...
* your type (your class) goes in an unnamed package.
*
* Java compiler automaticaly imports three packages:
*
* (1) the package with no name
* (2) the java.lang package
* (3) the current package
*/
package com.minte9.oop.packages;
import java.util.ArrayList;
public class Import {
public static void main(String[] args) {
ArrayList<Integer> list = new ArrayList<>();
list.add(1);
list.add(2);
System.out.println(list); // [1, 2]
}
}
Hierarchy
At first, packages appear to be hierarchial, but they are not.
/**
* Importing java.uitl.* imports all of the types ...
* in the java.util package but it does not import ...
* java.util.regex package
*/
package com.minte9.oop.packages;
//import java.util.*; // not used
//import java.util.regex.Matcher; // Look Here
import java.util.regex.Pattern;
public class Hierarchy {
public static void main(String[] args) {
Pattern p = Pattern.compile("Java");
java.util.regex.Matcher m = p.matcher("Java SE 8");
System.out.println(m.find()); // true
}
}
Last update: 233 days ago
