Unit 2 Vocabulary

defines a new data type (a classification). It is the formal implementation, or blueprint, of the attributes and behav­iors of the objects of that class.

class

a specific instance of a class with defined attributes.

object

data the object knows about itself

attributes

variables in a class that define the attributes for objects

instance variables

these define the behaviors or functions for objects to de­scribe what objects can do

methods

creates a new object and initializes its attributes (they have the same name as the class).

constructor

used to create a new object; every object is created using this keyword followed by a call to one of the class's constructors that initializes the object's attrib­utes

new

the constructor name followed by the parameter list

**constructor signature or header**

**the method name followed by the parameter list**

method signature or header

classes that create objects from primitive types, for exam­ple the Integer class and Double class

**wrapper classes**

used to indicate that an object reference doesn't refer to any object yet

null

**Returns the absolute value of an int value** 

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**(which means no negatives).**

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**Math method: int abs(int)**

Returns the value of the first parameter raised to the power of the second parameter.

**Math method: double pow(double, double)**

**Returns the positive square root of a double value.**

**method: double sqrt(double)**

**Returns a random double value greater than or equal to 0.0 and less than 1.0 (not including 1.0)!**

**Math.random()**

a list of the types and variable names for the arguments being passed to a method or constructor

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**parameter list**

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**creating multiple methods or constructors with the same name but different number or types of parameters.**

overloading

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**When you call a method or constructor and give it an argument, a copy of the argument's value is saved in the parameter variable.** 

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**call by value**

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**This is the error if you try to call an object method on an object variable whose value is null**

NullPointerException

**These methods must be called using an object name method name.**

**non-static or object method**

**These methods belong to a class and can be called by using the class name instead of creating an object.**

**static method**

**The value returned from a method to the calling method**

return value

objects of the String class that hold sequences of charac­ters.

strings

a number associated with a position in a string (or array)

index

String methods do not change the String object. Any method that seems to change a string actually creates a new string.

immutable

part of a string (the method will create a new string that contains a copy of part of the original string).

substring

returns the number of characters in a String object.

String method: int length()

returns the substring beginning at index from and ending at index (to - 1).

String substring(int from, int to)

returns substring(from, length()).

String substring(int from)

returns the index of the first occurrence of str; returns -1 if not found.

int index­Of(String str)

returns true if this (the calling object) is equal to other; returns false otherwise

boolean equals(String other)

returns a value < 0 if this is less than other; returns zero if this is equal to other; returns a value > 0 if this is greater than other.

int compareTo(String other)

returns a single character at position index

**substring(index, index+ 1)**

the automatic conversion of primitive types to their cor­responding object wrapper classes, for example int to Integer.

autoboxing

the automatic conversion of wrapper class to the primitive type, for example Integer to int.

unboxing

 moves the random number into a range starting from a minimum number where the range is the (max number - min number + 1)

(int)(Math.random()\*range) + minimum

**Returns the absolute value of a double value.**

**Math method: double abs(double)**