12/9/2020
Java Tips & Tricks. Know these before you step into the big… | by Sandumini Nayanathara | Javarevisited | Medium
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Java Tips & Tricks
Know these before you step into the big game
Sandumini Nayanathara
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Jul 22 · 7 min read
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Java Tips & Tricks. Know these before you step into the big… | by Sandumini Nayanathara | Javarevisited | Medium
Photo by Radu Florin on Unsplash
Java…. So you all reading this know that it is one of the most popular programming
languages around the world and designed to keep running on any stage incessantly. Be it
Windows applications, Web Applications, Mobile, Network, consumer electronic goods,
Java is everywhere. Java has witnessed consistent development in its programming
efficiency for decades and shows no sign of declining in popularity and, for that reason,
is worth learning for anyone willing to have a solid future as a developer. No matter
whether you are an expert or a newbie to Java familiarizing with good programming
practices will save tons of time. So let’s look into some java tricks and tips to save time,
optimize and improve code quality.
1. String Optimization
String objects are immutable in Java which means the String content is unchangeable
once created. Strings can be constructed by,
Directly assigning a String literal to a String reference
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Java Tips & Tricks. Know these before you step into the big… | by Sandumini Nayanathara | Javarevisited | Medium
By a constructor
String str1 = "I am a string";
String str2 = new String("I am a string via a constructor");
The first method is a better way to create Strings. Creating Strings using constructors
wastes memory space a lot as objects do not share storage even for the same content
while the first method does share storage for the same content.
String Literal vs String Object example — Image from NTU
Especially, avoid using the second method inside loops as by now you all can understand
new unnecessary objects will be created at each iteration wasting a great deal of storage.
Use StringBuffer or StringBuilder class if the content of a String is frequently modified as
these classes support mutable Strings.
2. String Concatenation
At the instance, you see String Concatenation, I know concatenating strings using ‘+’
operator is the first thing that pops into most of your heads. But did you know that it is
not the best and the only method to do the job? There are 4 methods to this.
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Java Tips & Tricks. Know these before you step into the big… | by Sandumini Nayanathara | Javarevisited | Medium
Using the ‘+’ operator
It’s the easiest way to concatenate multiple Strings but takes additional memory and
slows down the performance of your program. Especially if you are concatenating
multiple Strings within a loop. But this does not mean that you should avoid this
method. You can still use this for concatenating Strings in one statement.
String name = "S"+"a"+"m";
Using the concat() method
This method is hardly used. Performance is better than using ‘+’ operator but still, it’s
slower.
Using StringBuffer
This method is much faster than the above two. StringBuffer is synchronized for multithreaded operations which means this method is thread-safe. This is slower than
StringBuilder because of synchronized methods.
Append method of StringBuilder class
This is similar to StringBuffer except for that StringBuilder is not synchronized for multithreaded operations. If you are concatenating multiple Strings using a for-loop, then you
should use StringBuilder.
String name =
new StringBuilder().append("S").append("a").append("m").toString();
Now if I summarize this for you, when creating Strings from parts use
StringBuilder(single-threaded) or StringBuffer(multi-threaded). For String
Concatenation using for-loops use StringBuilder and for single statement String
Concatenation you can use the ‘+’ operator.
3. Use of Single and Double Quotes in Strings
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In brief, single quotes are used for literal chars while double quotes are for literal Strings.
In the below code snippet the letters ‘M’ and ‘Y’ will be the corresponding outputs.
System.out.println("M");
System.out.println('Y');
Now, what do you think of the code below?
System.out.println("M" +"Y");
System.out.println('M'+'Y');
The first output as you guessed is MY but second didn’t turn out to be MY, instead the
output appears to be 166. Adding two chars will return an int. Here the ASCII values of
the two chars will be added to return an int.
If you are wondering how to concatenate chars as a String, there are several ways to do
it.
System.out.println('M'+""+'Y');
System.out.println(""+'M'+'Y');
Both the above two methods will return the String MY. In addition, there are more
methods, like the StringBuffer and StringBuilder mentioned in the previous section.
4. Float vs Double
Both these data types are used to represent floating-point numbers and that double is
more precise is a well-known fact.
The use of double over float is highly recommended, especially, if you can’t guarantee
that your number is within floats’ specified range.
But note that double comes with a cost; it is expensive as it takes double the memory
space as of what float would take.
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Java Tips & Tricks. Know these before you step into the big… | by Sandumini Nayanathara | Javarevisited | Medium
5. Better to Avoid BigDecimal and BigInteger
You can also go with BigDecimal and BigInteger which is an exact way of representing
numbers.
If you are working with floating-point numbers with different precision or if you are
dealing with money where precision is a must, BigDecimal can be your pick. But it takes
more memory, it’s a bit difficult to program algorithms and slows down all calculations
drastically than using double.
So it is highly recommended to avoid using BigDecimal and also BigInteger, use them
only if there is no other way out.
6.Use Primitives Where Possible
Wrapper classes are a great deal of help for like converting primitive data types to
objects. Yet, primitives are simple, faster, and an easy way to avoid overhead. Thus, it is
better to use int instead of Integer or float instead of Float.
//using primitive data type
int num = 5;
//using wrapper class
Integer wrapNum = new Integer(5);
Furthermore, as Wrapper classes deal with objects, comparing them will not give desired
outcomes as it is with primitives. The reason for that is that it will end up comparing
objects instead of the content in those objects.
int num1 = 5;
int num2 = 5;
Integer wrapNum1 = new Integer(3);
Integer wrapNum2 = new Integer(3);
System.out.println(num1 == num2);
System.out.println(wrapNum1 == wrapNum2);
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The first print would be true but the second print would be false as the objects are being
compared there, not the values.
7. Handling Null Pointer Exception
Null pointer exception is a runtime exception that is thrown when an application is trying
to use an object reference with a null value.
String fruit;
spellChecker(fruit);
Here a null reference variable is passed as an argument of a method.
positionLocator(null);
In the above code snippet, null is directly passed to a function. In both these instances,
there is a high possibility of throwing the NullPointerException.
This exception can be fixed by using the try-catch block as well as by using the if-else
condition.
public class NullPointerExceptionExample{
public static void main(String args[]){
String fruit = "apple";
}
spellChecker(null);
positionLocator(null);
//Using a try-catch block
static void spellChecker(String fruit){
try{
System.out.println("Second character: "+fruit.charAt(0));
}
catch(NullPointerException e) {
System.out.println("NullPointerException thrown");
}
}
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//Using an if-else condition
static void positionLocator(String fruit){
if(fruit != null){
System.out.println("Second character: "+fruit.charAt(0));
}
else {
System.out.println("NullPointerException thrown");
}
}
}
8. Use Profilers to Optimize Your Code
Writing code and compiling it to get the required outputs is not just enough. We must
write codes with the best performance possible. To achieve that it is better if there is a
way to check what happens behind the code like, how memory is allocated, areas to
improve, and effects of using one coding approach to another. For this, we can use Java
Profilers.
Java Profiler is a tool that monitors Java bytecode constructs and operations at the JVM
level. Using these profilers we can find out the performance, memory usage, memory
leaks, etc in our programs, and then we can easily find out what to change, optimize or
eliminate in the code.
There are a number of profilers available like JProfiler, XRebel, and New Relic but each of
these profilers has unique characters and is better for a certain aspect of performance
bugging. Therefore, profilers should be selected according to the level of analysis
needed, and for better results, you can use a combination of multiple profilers.
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Memory Allocation of an Application — Image from Stack Overflow
You can find more on Java Profilers here.
9.Array vs ArrayLists
The main difference between these two is that an Array is of fixed size so once you have
created an Array you cannot change it but the ArrayList is not of fixed size. You can
create instances of ArrayLists without specifying its size. So if you create such instances
of an ArrayList without specifying its size Java will create an instance of an ArrayList of
default size.
Once an ArrayList is full it re-sizes itself. In fact, an ArrayList is internally supported by
an array. So when an ArrayList is resized it will slow down its performance a bit as the
contents of the old Array must be copied to a new Array.
At the same time, it’s compulsory to specify the size of an Array directly or indirectly
while creating it. And also Arrays can store both primitives and objects while ArrayLists
only can store objects.
I hope this article was some sort of help to you. Hope to bring more articles soon. Thank
you for reading.
Resources
Java Performance Tuning from Stackify
Java Programming Best Practices and Tips from JavaCodeGeeks
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12/9/2020
Java Tips & Tricks. Know these before you step into the big… | by Sandumini Nayanathara | Javarevisited | Medium
Java String is Special from NTU
How to Resolve NullPointerException from edpresso
4 ways to concatenate Strings in Java from Java67
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