STRING CLASS

PROGRAMMING

​11 ICT

CLASS STRINGS
and PROGRAM STYLE

REVIEW

Answer the questions by arranging the line of code/s to get the output or correct a simple line of code.
Please also check if the CASING is right.

Open Ended

Arrange the given line of code:

public static main String ([] args)

Open Ended

Arrange and/or change the given line of code to make it correct. (if you think there is a missing part, add it to the program code)

int = myInteger 2.0

Open Ended

Arrange and/or change the given line of code to make it correct. (if you think there is a missing part, add it to the program code)

System.Print('HelloWorld')

Open Ended

What is the output?

public class Multiply{

public static void main (String [] args)

double y=10*1+10;

System.out.println(z)}}

Open Ended

Arrange the 3rd line of code to make it correct:

public class Multiply{

public static void main (String [] args){

double y=10*1+10;

System.out.println(z);}}

ANALYZE:

When do we normally use " " and ' ' ?

ANALYZE:

In language: direct quotes, dialogue, titles of short works, the emphasis of certain words, and separating nicknames from given names.
In programming?

​" "

ANALYZE:

In language: used to replace double quotation marks when they’re inside of other double quotation marks
In programming?

​' '

CLASS STRING

BUZZ BUZZ TO ANSWER

Be READY to answer during our discussion!
You can click the buzzer when you're done typing the correct answer.

ANALYZE:

Can you use " " inside another " "?

BUZZ BUZZ TO ANSWER

Can you use " " inside another " "?

ANSWER:

YES

Escape Sequences

\”  = Double Quote
\’ = Single Quote
\\ = Backslash
\n = New line (beginning of the next line)
\r = Carriage return (beginning of the current line)
\t = Tab

CLASS STRING

-String

-Used to store and process strings of characters.

-When used to declare: String VariableName;

-Use of  double quotation     “      ”.

-The quoted string is a value of type String.

BUZZ BUZZ (type your answer then buzz)

Type a line of code for displaying/printing/result:
"Hello ICT!"

NOTE: Just a single line for printing/displaying the output.

ANSWER:

System.out.println(“\"Hello ICT!\"”);

BUZZ BUZZ (type your answer then buzz)

• Declare Food to be the name of the String Variable

• Set the value of Food as "Chicken and Pork Adobo"

  How will you write it using Java Syntax/code?
  

NOTE: Just a single line for declaring variable.

CONCATENATION OF STRINGS

• + sign becomes or sometimes called concatenation operator

• When you use the + operator on two strings, the result is the string obtained by connecting the two strings to get a longer string.

CONCATENATION OF STRINGS

Can we use concatenation when combining a variable and a string?

BUZZ BUZZ TO ANSWER

Can we use concatenation when combining a variable and a string?

ANSWER:

YES

String noun = “Strings”;
String sentence;

sentence = noun + “are cool.”;
System.out.println(sentence);

What is the output?

BUZZ BUZZ TO ANSWER

String noun = “Strings”;
String sentence;

sentence = noun + “are cool.”;
System.out.println(sentence);

ANSWER:

Stringsare cool

BUZZ BUZZ TO ANSWER

System.out.println(“100” + 42);
System.out.println(100 + 42);

What is the output?

ANSWER:

10042
142

TERMS TO REMEMBER

• are entities that store data and can take actions.

Objects

• the name for a type whose values are objects.

Class

• the information in parenthesis

Argument

• the actions that an object can take.

Methods

• called sending a message to the object.

Invoking a method

String Methods

• A string method is called (invoked) by writing a String object, a dot, the name of the method, and finally a pair of parenthesis that enclose any arguments to the method.

Example:

String greeting = “Hello”;
//int count = greeting.length();

System.out.println(“Length is ” + greeting.length());
What is the output?

BUZZ BUZZ TO ANSWER

String greeting = “Hello”;
//int count = greeting.length();

System.out.println(“Length is ” + greeting.length());

ANSWER:

Length is 5

Here are some METHODS in the Class String

int length()

• returns the length of the calling object (which is a string) as a value of type int.

int length()

Example:
String greeting = “Hello ”;
greeting.length() displays ?
Output:

int length()

Example:
String greeting = “Hello ”;
greeting.length() displays ?
Output:
6

boolean equals(Other_String)

• returns true if the calling object string and the Other_String are equal. Otherwise, returns false.

boolean equals(Other_String)

Example:
String greeting = “Hello”;
greeting.equals(“Hello”) returns ?
greeting.equals(“hello”) returns ?
greeting.equals(“Goodbye”) returns ?

Output:

?
?
?

boolean equals(Other_String)

Example:
String greeting = “Hello”;
greeting.equals(“Hello”) returns ?
greeting.equals(“hello”) returns ?
greeting.equals(“Goodbye”) returns ?

Output:

TRUE
FALSE
FALSE

boolean equalsIgnoreCase(Other_String)

• returns true if the calling object string and the Other_String are equal, considering uppercase and lowercase versions of a letter to be the same. Otherwise, returns false.

boolean equalsIgnoreCase(Other_String)

• Example:
  String greeting = “mary! ”;
  greeting.equalsIgnoreCase("Mary!") returns?
  Output:

boolean equalsIgnoreCase(Other_String)

Example:
String greeting = “mary! ”;
greeting.equalsIgnoreCase("Mary!")
Output:

True

String toLowerCase()

• returns a string with the same characters as the calling object string, but with all letter characters converted to lowercase.

String toLowerCase()

Example:
String greeting = “Hi Mary! ”;
greeting.toLowerCase() returns?
Output:

String toLowerCase()

Example:
String greeting = “Hi Mary! ”;
greeting.toLowerCase() returns?
Output:
hi mary!

String toUpperCase()

• returns a string with the same characters as the calling object string, but with all letter characters converted to uppercase.

String toUpperCase()

Example:
String greeting = “Hi Mary! ”;
greeting.toUpperCase() returns?
Output:

String toUpperCase()

Example:
String greeting = “Hi Mary! ”;
greeting.toUpperCase() returns?
Output:
HI MARY!

String trim()

• returns a string with the same characters as the calling object string, but with leading and trailing white space removed.

• white space-blank space, tab, new line

String trim()

Example:
String pause = “     Hmm    ”;
pause.trim() returns ?
Output:

String trim()

Example:
String pause = “     Hmm    ”;
pause.trim() returns ?
Output:
Hmm

char charAt(position)

• returns the character in the calling object string at the Position.

• Position are counted 0, 1, 2, etc.

char charAt(position)

Example:
String greeting = “Hello!”;
greeting.charAt(0) returns ?
greeting.charAt(1) returns ?
Output:

char charAt(position)

Example:
String greeting = “Hello!”;
greeting.charAt(0) returns ?
greeting.charAt(1) returns ?
Output: H
e

String substring(start/position)

• returns the substring of the calling object string starting from position Start through to the end of the calling object.

String substring(start/position)

Example:
String sample = “AbcdefG”;
sample.substring(2) returns ?
Output:

String substring(start/position)

Example:
String sample = “AbcdefG”;
sample.substring(2) returns ?
Output:
cdefG

String substring(start, end)

• returns the substring of the calling object string starting from position Start through but not including, position End of the calling object.

String substring(start, end)

Example:
String sample = “AbcdefG”;
sample.substring(2, 5) returns ?
Output:

String substring(start, end)

Example:
String sample = “AbcdefG”;
sample.substring(2, 5) returns ?
Output:
cde

int indexOf(A_String)

• returns the index (position) of the first occurrence of the string A_String in the calling object string. Returns -1 if A_String is not found.

int indexOf(A_String)

Example:
String greeting = “Hi Mary!”;
greeting.indexOf("Mary") returns ?
greeting.indexOf("Sally") returns ?
Output:

int indexOf(A_String)

Example:
String greeting = “Hi Mary!”;
greeting.indexOf("Mary") returns ?
greeting.indexOf("Sally") returns ?
Output: 3
-1

int lastIndexOf(A_String)

• returns the index (position) of the last occurrence of the string A_String in the calling object string. Returns -1 if A_String is not found.

int lastIndexOf(A_String)

Example:
String greeting = “Mary, Mary, Mary you are sweet”;
greeting.indexOf("Mary") returns ?
greeting.lastIndexOf("Mary") returns ?
Output:
0
12

RECALL OF METHODS

• int length()

• boolean equals(other_string)

• boolean equalsIgnoreCase(other_string)

• String toLowerCase()

• String toUpperCase()

• String trim()

RECALL OF METHODS

• char charAt(position)

• String substring(Start)

• String substring(Start, End)

• int indexOf(A_String)

• int lastIndexOf(A_String)

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Check our activity there. Submit your output.
A student will explain the answer in class.

COMMENTS

• Two ways to insert comment:

//comment  and   /*  comment  */

• Line comments // (for comments meant only for the code writer or for programmers who modifies the code.

• Block comments /* */ (for line breaks and documentation)

INDENTING

• GENERAL RULE: easy to understand and easy to follow.

Questions?

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PERFORMANCE TASK AND WRITTEN ACTIVITY