Difference between revisions of "Java/C2/Strings/English"

Welcome

Learning Outcomes

create strings, add strings and perform basic string operations like converting to lower case and upper case.

Tools Used

Ubuntu 11.10, JDK 1.6 and

Eclipse 3.7'

Prerequisites

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Strings

Before starting with Strings, we will first see the character data type.

Let us now switch to eclipse

Eclipse should contain the following code

public class StringDemo{

public static void main(String[] args){

}

}

We have created a class StringDemo and added the main method.

char star = '*';

This statement creates a variable with name star and of the type char.

It can store exactly one character.

Let us print a word using a few characters.

char c1 = 'c';

char c2 = 'a';

char c3 = 'r';

char c1 equal to c

char c2 equal to a

char c3 equal to r

We have created three characters to make the word car.

Now let us use them to print the word.

System.out.print(c1);

System.out.print(c2);

System.out.print(c3);

Save and Run.

Point to output

System.out.print(c1);

System.out.print(c2);

System.out.print(c3);

Please note that I’m using print instead of println so that all the characters are printed on the same line.

save the file and run it.

As we can see, the output is as expected.

But this method only prints the word but does not create one.

To create a word, we use the String data type.

Let us try it out.

String greet = “Hello Learner”;

Type String greet equal to Hello Learner in quotes;

Note that the S in the data type String is in uppercase.

We have use double quotes instead of single quotes as delimiters

This statement creates a variable greet that is of the type String

Now Let us print the message.

System.out.println(greet);

Save the file run it .

Point to output

System.out.println(greet);

Save the file and run it As we can see, the message has been stored in the variable and it has been printed.

Strings can also be added in Java.

let us see how to do so.

We'll store the name in a different variable.

String name = “Java”;

String msg = greet + name;

change println(greet) to println(msg)

Save and Run.

Point to output

String name equal to “Java”;

Now we’ll add the strings to make a message

String msg equal to greet plus name;

change println(greet) to println(msg) save the file and run it.

We can see that the output shows the greeting and the name.

But there is no space separating them.

char SPACE = ' ';

Change greet + name to greet + SPACE + name

Save and Run.

Point to output

char SPACE equal to ' ';

Note that I have used all uppercase letters in the variable name so that it is clear.

You can change it as you want.

Now let us add the space to the message.

greet plus SPACE plus name

save the file and run it

Now we can see the output is clear and as expected.

Let us look at a few basic string operations.

Change “Java” to “jAvA”

Save and Run.

Point to output

and a word “java” to uppercase.

Often, when users give input, we have values like this, in mixed case.

So Let us run the file to see the output.

As we can see t he output is not clean.

Let us use the String methods to clean the input.

greet = greet.toLowerCase();

name = name.toUpperCase();

Save and Run.

Point to output

greet equal to greet.toLowerCase();

This statement converts each character of the string greet to lowercase

name equal to name.toUpperCase();

This statement converts each character of the string name to uppercase.

Save the file and Run  it.

As we can see, the output is now clean after we have used the String methods.

There are many more String methods and

We'll discuss them as we move on to complex topics.

Slide 6

Summary

In this tutorial we have learnt

- how to create strings and addstrings

- few string operations like converting to lower case and upper case

- Read about the concat method of Strings in Java. - Find out how is it different from adding strings.

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