Why Comparison Integer Using == Inwards Coffee Five Is Bad?

Java five introduced auto-boxing which automatically converts int to Integer as well as because of that many Java developers started writing code for comparing int variable to Integer object as well as Integer to Integer using == operator. You should avoid that because it tin create subtle bugs inward your programme because it solely industrial plant for a detail gain of integers as well as non for all. There is or so other occupation also when you lot compare int variable to Integer object using == operator, the Integer object is converted to a primitive value. This tin throw zilch pointer exception if the Integer object is null, which tin crash your program. Now when you lot compare 2 Integer object using a == operator, Java doesn't compare them yesteryear value, only it does reference comparison. When agency fifty-fifty if the 2 integer has the same value, == tin provide faux because they are 2 dissimilar objects inward the heap. That's why you lot should purpose equals() method to compare objects.

There is ane to a greater extent than request which makes affair tricky, caching of integer objects yesteryear Integer.valueOf() method. What this hateful is that your programme volition operate for or so input only non for others.

This happens because automobile boxing uses Integer.valueOf() method to convert Integer to int as well as since method caches Integer object for gain -128 to 127, it provide same Integer object inward heap, as well as that's why == operator provide truthful if you lot compare 2 Integer object inward the gain -128 to 127, only provide faux afterwards, causing bug.

Before Java 1.4 that was non a occupation because at that spot was no autoboxing, so you lot ever knew that == volition banking concern fit reference inward heap instead of value comparison.

Comparing Integer object alongside == inward Java

Some of the JVM cache objects of or so wrapper shape e.g. Integer from -128 to 127 as well as provide same object which if compare via “ ==” tin provide truthful only after this gain this validity doesn't operate as well as to arrive worse this necessitate is JVM subject so amend avoid this form of banking concern fit as well as purpose equals() method. e.g.

Integer i1 = 260; Integer i2 = 260;  if (i1 == i2) {     System.out.println("i1 as well as i2 is equal"); } else {    System.out.println("i1 as well as i2 is non equal "); }

Here you lot volition virtually in all probability teach "i1 as well as i2 is non equal " at to the lowest degree inward my machine.
because inward this case, unboxing performance is non involved. The literal 260 is boxed into 2 dissimilar Integer objects ( in ane lawsuit to a greater extent than it varies betwixt JVM to JVM) , as well as and then those objects are compared alongside ==. The outcome is false, equally the 2 objects are dissimilar instances, alongside dissimilar retention addresses. Because both sides of the == appear comprise objects, no unboxing occurs.

Integer i1 = 100; Integer i2 = 100;  if (i1 == i2) {     System.out.println("i1 as well as i2 is equal"); } else {    System.out.println("i1 as well as i2 is non equal "); }

Here, virtually in all probability you lot volition teach the text "i1 as well as i2 is equal".
Because int values from -127 to 127 are inward a gain which virtually JVM volition similar to cache so the VM truly uses the same object instance (and thus retention address) for both i1 as well as i2. As a result, == returns a truthful result.

This is really indeterministic as well as solely shown yesteryear representative since or so JVM practise optimization at for certain integer value as well as sweat to provide same object every fourth dimension only its non guaranteed or written behavior.

So best is to avoid this form of code inward postal service Java 1.5 as well as instead purpose equals() method to compare Integers inward Java, which is to a greater extent than deterministic as well as correct.

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