If we want to use any predefined class or user defined class or interface or enum which is present in a package we need to import those entire packages or those classes so that we can use those classes present inside the package.

import packagename.ClassTest;
import packagename.*;
For example if we want to read some data from keyboard we can use scanner class present in util package.
import java.util.Scanner;
We can import everything inside a package by using .*
import java.util.*;
Without importing want to use that class then code seems to like this

package com.instanceofjava;
class A{
public static void main(String [] args){
int number;
java.util.Scanner in = new java.util.Scanner(System.in);
System.out.println("Enter a number to check even or odd");
number=in.nextInt();
}
}

if we use import no need to mention class name in declaration

package com.instanceofjava;
import java.util.Scanner;
class A{
public static void main(String [] args){
int number;
Scanner in = new Scanner(System.in);
System.out.println("Enter a number to check even or odd");
number=in.nextInt();
}
}

Static import:

Normal imports will import the all the classes so that we can use them. similarly static imports will import all static data so that can use without class name.
Static imports introduced in Java 5.
Lets see one program without static import.

Without Static Import:

package com.instanceofjava;
class StaticImport{
public static void main(String [] args){
System.out.println(Math.PI); //3.141592653589793
System.out.println(Integer.MAX_VALUE);//2147483647
System.out.println(Integer.parseInt("123"));//123
}
}

Using Static import:

static import in java with example:

package com.instanceofjava;
import static java.lang.Integer.*;
import static java.lang.Math.*;
class StaticImport{
public static void main(String [] args){
System.out.println(PI); //3.141592653589793
System.out.println(MAX_VALUE);//2147483647
System.out.println(parseInt("123"));//123
}
}

static imports in java 1.5 examples:

Importing Math class:

package com.instanceofjava;
import static java.lang.Math.*;
class StaticImport{
public static void main(String [] args){
System.out.println(PI); //3.141592653589793
double square;
double d1 = 3.0;
double d2 = 4.0;
square = sqrt(pow(d1, 2) + pow(d2, 2));
System.out.println(square);
}
}

Importing System class:

package com.instanceofjava;
import static java.lang.System.out;
class StaticImport{
public static void main(String [] args){
out.println("Good morning, " + "java2s");
out.println("Have a day!");
}
}

Importing User defined classes:

package com.instanceofjava;
class Colors{
public static int white = 1;
public static int black = 2;
public static int red = 3;
public static int blue = 4;
public static int orange = 5;
public static int grey = 6;
public static int green =7;
}

package com.instanceofjava;
import static com.instanceofjava.Colors.*;
class StaticImportDemo{
public static void main(String [] args){
System.out.println(white );//1
System.out.println(blue);//4
}
}

Arrays and Collections:

package com.instanceofjava;
import static com.instanceofjava.Colors.*;
class StaticImportDemo{
public static void main(String [] args){
int[] array = new int[] {5, 4, 6, 3, 2, 1};
sort(array);
for (int i = 0; i < array.length; i++) {
System.out.print(array[i]+" ");
}
ArrayList al= new ArrayList();
al.add(1);
al.add(12);
al.add(3);
al.add(2);
sort(al);
Iterator itr= al.iterator();
while(itr.hasNext()){
System.out.printl(itr.next()+" ");
}
}
}

OutPut:

1 2 3 4 5 6
1 2 3 12

Advantages and Disadvantages of Static imports in java:

One of the advantage of using static imports is reducing keystrokes and re usability.
System.out.println() ; we can write as out.println() . But using eclipse short cut syso (ctrl+sapce) gives System.out.println() faster than static imports usage.
And there may be a chance of complexity in readability.
If we use class name before method like Math.sqrt() then can understand easily that method belongs to particular class . with static imports reduces readability.
One more disadvantage is naming conflicts.
If we use Integer.Max_value we cannot use Float.Max_value

Java programming interview questions

Static import In java

Static import:

Without Static Import:

Using Static import:

static imports in java 1.5 examples:

Importing Math class:

Importing System class:

Importing User defined classes:

Arrays and Collections:

Advantages and Disadvantages of Static imports in java:

Instance Of Java

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Static import In java

Static import:

Without Static Import:

Using Static import:

static imports in java 1.5 examples:

Importing Math class:

Importing System class:

Importing User defined classes:

Arrays and Collections:

Advantages and Disadvantages of Static imports in java:

Instance Of Java

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