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Not it's look at string concatenation string concatenation involves concatenating strings together that

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is with joined strings together.

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We all know that a plus operator can be used for that.

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And here is an example.

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If you want to additionally concatenate a pneumatic 125.

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We could have done this Alternatively you can also do this.

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That is we simply add the indigent 125 undergrad we are took on what administering.

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So the plus operator gives precedence to a string operation.

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And so any non string or print will be automatically converted to a string.

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So it's a little bit like the mixed up operations rule where smaller type operand is automatically promoted

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with a larger type.

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And this because you can think of string as the larger type not want to also concatenate a double value

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.

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We can do this not that here the last two numeric values are not honored but they are simply concatenated

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.

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This is because there is no parenthesis and there is only a single operator in the expression.

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So if you recall in this because the expression is evaluated from left to right.

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So faster two strings.

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How long will it be concatenated and then press will be applied on the string Hello world.

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The numeric 125.

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The resulting string will then be finally concatenated with a numeric only 5.5.

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Hello or if he had this exhibition we're numerics or more with a friend than the two numeric values

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will be added first as evaluation happens from left to right.

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The resulting value will then be concatenated with the following strings.

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String concatenation can also be performed using string builder and string buffer classes from the Djala

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Dr. Lang package while string class is immutable.

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These two classes allow us to mutate strings that is these two classes allow their contents to be changed

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let's not look at string builder class it was introduced in Jollof I on here is an example of its usage

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Foster string will that object is created and then it's a benefit that is involved to append new content

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.

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So fast the string hello is honored and then the string world is up undecorated next a single statement

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is used to append two more strings not that each append gone returns a reference to the current object

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which is allowing in multiple append calls in the same state and finally posting method is invoked which

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returns a string that is initialized with a character sequence in the string builder so string as has

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the entire text Hello world.

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Good morning string will that also has many other matters.

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And here are a few of them.

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You can use that matter to know the length of the string constructor.

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So.

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Need math that can be used to delete characters between two indices Similarly there are methods for

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inserting content or to specify an index.

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There is also a method to reverse a string.

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Finally there is also a method to replace certain substrings with the specified strings.

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Most of the time you will be using a pen and that boosting matters at the end of the lesson will be

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a short term or maybe we'll try out some of these methods also as you can see unlike string class string

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will there is more to have happen and does it allows us to modify its content.

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Finally string builder is not synchronized synchronization is a concurrency concept and you look at

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it later when studying concurrency.

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But that just gives you an idea if the same string builder object is shared across two threads then

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one thread can modify the contents of the object when the other is already modifying the seeing content

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.

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So there is a simultaneous modification of the content and this can be good data corruption issues and

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this can happen because string builder is not synchronized but if synchronization is critical it can

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be taken care of externally and that we will see Randstad in concurrency know before signing a bill

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that was introduced in July 5 string buffer was being used and it works just like string builder that

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is it is like String class but can be modified.

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However with the introduction of string builder class it is recommended to use string builder as it

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is faster than string Barbar.

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The main reason is because string before is synchronized and synchronization slows down the program

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.

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This is because synchronization has to ensure that at any particular time only one thread is modifying

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string first content.

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Well synchronization is critical in the context of multi-threading.

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It was found to be an overhead in the context of using string buffer.

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This is because string buffer was mostly being used by a single thread and programmers were not usually

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sharing it across tracks.

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So the language designers decided to introduce string builder and also allowed developers to use it

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as a drop in replacement for string buffer string buffer is being used by only a single thread to ensure

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this string builder was designed to have an API that is compatible with string buffer.

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So just look on the Java docs for both these classes and you'll be able to see the similarities non-Disney

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a short term or string concatenation

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in the interest of time I'm going to show this to mind my eclipse the I and we're going to try out all

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three weeks off concatenating strings that is using press operator then the two class a string builder

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string buffer.

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OK so let's begin with this plus all pricker So let's just create a string and let's just concatenate

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two strings.

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Hello world.

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It's just print this

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I mean just from this and it's printing out here next let's create string buffer so let's create a string

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but for instance

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and we can pass this same string reference S here so that where we are initialising string buffer with

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this.

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So there is a constructor for that next letter.

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A pen couple of our new strings to this to the string Hello world.

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So let's just call a band met they're and that's been the key word good and since then returns a reference

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to the cut on String object to the current string buffer object we can use one more up and method here

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so we can change it this way as we have seen earlier in the slightest and that's a morning and let's

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put a smiley here.

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And that's it.

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Now let's just grand

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the strength so there's just as be taught to string that arrogance does a string that frequences string

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going on.

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That's also print the land I need to say the it so now let's print this.

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So as you can see as B is now.

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Hello world.

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Good morning.

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On the left is 29.

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OK.

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So that's the length of the string that we construct so far.

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Now we also have a couple of other matters like we discussed about other methods like delete and insert

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.

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Let's just try or delete an insert now.

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So let's say we want to delete contactors starting with the next one and ending with the next five.

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So here one is inclusive but and five is exclusive so.

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So we wanted to lead the characters from starting from one to the index for OK not five.

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So let's again reprint this the same length and distrain And as you can see the characters E L L O.

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Which is it starts with the index one and an index for you know are are just removed are just deleted

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.

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So since four characters have been deleted the plant is now 25.

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Now let's insert a couple of garters.

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So let's just set it s b dark.

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Insert one so you want to insert the next one and say you want to next the string you write so that

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rate will be previous her alone I was going to be here.

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So that's just then the message is once again be the string Underland.

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Now you can see that the characters yway got added here.

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So we have hello.

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Hey hey.

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Well good morning Underland is not only seven so that's how you can you know you can mutate the string

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with just a string.

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It is immutable.

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But here when you use string before we can mutate string and we said that with string after five point

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off a dollar fine you know we can use a shingle as it is much more efficient.

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So we can have it like this.

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So all we need to do is just replace string buffer with string builder and everything works the same

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.

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So the language designers the you know they make sure that you know that the API is exactly identical

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so they have to support all the networks on you know on them at their signatures so that we can use

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it as a drop in replacement.

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You know instead of staring before and using string builder is much faster if synchronization is not

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needed.

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OK.

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So that's important.

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So we looked at both plus plus singular osting buffer before string builder or string buffer.

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Next we're going to look at an item from Effective Java and it is related to a string concatenation

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and it specifically talks about String about the plus operator on some performance implications that

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are honored.

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So that would be the next lesson.

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OK right then.

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Thank you and happy coding.