Java 9 Objects Class additional methods null pointer check index and length
This Java code demonstrates the usage of new methods introduced in Java 9 in the Objects class. The class java9Additionals contains a method objectsClassModificationsInJava9 that showcases the functionality of these methods. Here's a detailed explanation:
Package and Imports
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package com.nuhman.coding.test;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Objects;
The package declaration indicates that this class is part of the com.nuhman.coding.test package.
The java.util package is imported to use Arrays, Collections, List, and Objects classes.
Class Definition
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public class java9Additionals {
The class java9Additionals is declared as public, meaning it can be accessed from outside its package.
Method: objectsClassModificationsInJava9
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public static void objectsClassModificationsInJava9 (List<String> stringList) {
This method is declared as public static, meaning it can be called without creating an instance of the class. It takes a single parameter, stringList, which is a List of String objects.
Using requireNonNullElse
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// The new methods in Java 9
// 1 . requireNonNullElse method
List<String> strList = Objects.requireNonNullElse(stringList, Collections.EMPTY_LIST);
System.out.println(strList);
Objects.requireNonNullElse(stringList, Collections.EMPTY_LIST) returns stringList if it is non-null; otherwise, it returns Collections.EMPTY_LIST (an empty list). This method provides a simpler alternative to manually checking for null.
Using requireNonNullElseGet
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// 2 . requireNonNullElseGet method
strList = Objects.requireNonNullElseGet(stringList, List::of);
System.out.println(strList);
Objects.requireNonNullElseGet(stringList, List::of) returns stringList if it is non-null; otherwise, it returns a new empty immutable list created by List::of.
Using checkIndex
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// 3 . checkIndex method
int checkIndex = Objects.checkIndex(strList.size(), 1);
System.out.println(checkIndex);
// replaces if(strList.size()==1) throws exception
Objects.checkIndex(strList.size(), 1) checks if the index 1 is within the bounds of strList. It returns the index if valid; otherwise, it throws IndexOutOfBoundsException.
Using checkFromToIndex
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// 4 . checkFromToIndex method
int startIndex = 0;
int endIndex = 1;
checkIndex = Objects.checkFromToIndex(startIndex, endIndex, 1);
System.out.println(checkIndex);
Objects.checkFromToIndex(startIndex, endIndex, 1) checks if the range from startIndex to endIndex is within the bounds of a list of size 1. It returns the startIndex if valid; otherwise, it throws IndexOutOfBoundsException.
Using checkFromIndexSize
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// 5 . checkFromIndexSize method
startIndex = 2;
endIndex = 4;
checkIndex = Objects.checkFromIndexSize(startIndex, endIndex, 6);
System.out.println(checkIndex);
Objects.checkFromIndexSize(startIndex, endIndex, 6) checks if the sublist starting at startIndex with endIndex length is within the bounds of a list of size 6. It returns the startIndex if valid; otherwise, it throws IndexOutOfBoundsException.
Main Method
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public static void main(String[] args) {
objectsClassModificationsInJava9(null);
objectsClassModificationsInJava9(Arrays.asList("str", "str2"));
}
The main method tests objectsClassModificationsInJava9 with two scenarios:
Passing null to the method.
Passing a list with two strings: "str" and "str2".
In summary, this code demonstrates the new Objects methods introduced in Java 9, which provide more concise and readable ways to handle common tasks like null-checking and index validation.
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