AP Computer Science AP Computer Science editionedition

Review 1Review 1

ArrayLists While loops String Methods

Methods Errors

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ArrayLists - 100ArrayLists - 100

Refer to an element in an array list.

ArrayLists - 200ArrayLists - 200

Add an element to the beginning of an array list

ArrayLists - 300ArrayLists - 300

Remove the last element in an array list

ArrayLists - 400ArrayLists - 400

Sum up all elements in an array list using an enhanced for loop

ArrayLists - 500ArrayLists - 500

Using a for loop, print out all the elements in reverse order

While loops - 100While loops - 100

What is the first step in creating a while loop?

While loops - 200While loops - 200

When should you use a while loop instead of a for loop?

While loops - 300While loops - 300

How many times would you loop here?int x = 10;while (true){ if ( x > 15) break; else x -= 1;}

While loops - 400While loops - 400

What would I code in the following loop header to break out if the score was not between 0 and 100?

while ( _____________ ){ …….}

While loops - 500While loops - 500

Using a while loop, continue printing out the elements in an integer array until the integer is greater than 10 and its an even number.

Strings - 100Strings - 100

Returns how many characters are in the string

Strings - Strings - 200200

Returns true or false depending if the Strings contain the same word

Strings - Strings - 300300

Allows the programmer to take pieces of strings and save them into new strings

Strings - Strings -

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This method uses lexicographical analysis

Strings - Strings -

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Allows the programmer to combine strings to form a single new string.

Methods - Methods - 100100

A specialized method that constructs new objects

Methods - Methods - 200200

A method that returns a value to the caller

Methods - Methods -

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The information that is passed to the method

Methods - Methods -

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What are the variables called that track key information about an object?

Methods - 500Methods - 500

A method in a class that is not used for an individual object

Errors -100 Errors -100

These extremely common errors will prevent the program from compiling

Errors - Errors - 200200

These can cause the program to crash while running

Errors - Errors - 300300

This occurs when the programmer misunderstands the program

Errors – Errors – 400400

This occurs when a call to an array or a String has exceeded its length

Errors – Errors – 500500

This occurs when an object name has been declared, but not initialized

Thanks Thanks

ArrayLists – 100 (solution)ArrayLists – 100 (solution)

Refer to an element in an array list.

ArrayList<Integer> aList;aList = new ArrayList<Integer>();aList.get(0) refers to first elementaList.get(i) refers to the ith element

ArrayLists – 200 (solution)ArrayLists – 200 (solution)

Create an element at the beginning of an array list

ArrayList<Integer> aList;aList = new ArrayList<Integer>();aList.add(0, 25); //creates an element with value 25 and shifts all other elements up

ArrayLists – 300 (solution)ArrayLists – 300 (solution)

Remove the last element in an array list

If (aList.size() > 0) aList.remove(aList.size() – 1);

ArrayLists – 400 (solution)ArrayLists – 400 (solution)

Sum up all elements in an array list using an enhanced for loop

int sum = 0;for ( int e : aList ){ sum += e;}

ArrayLists – 500 (solution)ArrayLists – 500 (solution)

Using a for loop, print out all the elements in reverse order

for(int i = aList.size()-1; i >= 0; i--){ System.out.println(aList.get(i));}

While loops – 100 (solution)While loops – 100 (solution)

What is the first step in creating a while loop?

Determine what is true when the loop ends. This is usually easier than determine what needs to be true to keep looping.

While loops – 200 (solution)While loops – 200 (solution)

When should you use a while loop instead of a for loop?

Use a while loop instead of a for loop when you don’t know how many times you need to loop (indefinite loop).

While loops – 300 (solution)While loops – 300 (solution)

How many times would you loop here?int x = 10;while (true){ if ( x > 15) break; else x -= 1;}

Infinitely or until the computer ran out of memory.

While loops – 400 (solution)While loops – 400 (solution)

What would I code in the following loop header to break out if the score was not between 0 and 100?

while ( score >= 0 && score <= 100 ){ …….}

While loops – 500 (solution)While loops – 500 (solution)

Using a while loop, continue printing out the elements in an integer array until the integer is greater than 10 and its an even number.int i = 0;while ( a[i] <= 10 || a[i]%2 == 1 ){

System.out.println( a[i] ); i++;}

Strings – 100 (solution)Strings – 100 (solution)

Returns how many characters are in the string

s.length();

Strings – 200 (solution)Strings – 200 (solution)

Returns true or false depending if the Strings contain the same word

s.equals(word)

if (s.equals(“cat”){ ……}

Strings – 300 (solution)Strings – 300 (solution)

Allows the programmer to take pieces of strings and save them into new strings

String part = s.substring(2,5);

Remember that subtracting 5-2 = 3 tells you that the substring is 3 characters.

Strings – 400 (solution)Strings – 400 (solution)

This method uses lexicographical analysis

s.compareTo(“cat”);

if it returns -1 then s < “cat”If it returns 0 then s = “cat”If it returns 1 then s > “cat”

Strings – 500 (solution)Strings – 500 (solution)

Allows the programmer to combine strings to form a single new string.

Concatenation:String fullName = firstName + “ “ + lastName;

Methods – 100 (solution)Methods – 100 (solution)

A specialized method that constructs new objects

The Constructor method has the same name as the class and is used to construct the object. One of its main functions is to initialize the instance variables.

Methods – 200 (solution)Methods – 200 (solution)

A method that returns a value to the caller

A Return method returns a value to the calling class. The return statement is used to return the value and its data type must match that specified in the method’s signature line.

Methods – 300 (solution)Methods – 300 (solution)

The information that is passed to the method

Parameters are passed to the method. There can be multiple parameters separated by commas.

Methods – 400 (solution)Methods – 400 (solution)

What are the variables called that track key information about an object?Instance variables store the important information about an object. They are normally private variables and are declared outside of your methods at the top of the class.

Methods – 500 (solution)Methods – 500 (solution)

A method in a class that is not used for an individual object

Static methods are methods that don’t operate against individual objects. In fact, you don’t have to instantiate the object in order to use them.

Errors – 100 (solution)Errors – 100 (solution)

These extremely common errors will prevent the program from compiling

Syntax errors

Errors – 200 (solution)Errors – 200 (solution)

These can cause the program to crash while running

Runtime errors

Errors – 300 (solution)Errors – 300 (solution)

This occurs when the programmer misunderstands the program

Logic errors

Errors – 400 (solution)Errors – 400 (solution)

This occurs when a call to an array or a String has exceeded its length

Index out of bounds errors

Errors – 500 (solution)Errors – 500 (solution)

This occurs when an object name has been declared, but not initialized

Null pointer exception