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36 Cards in this Set
- Front
- Back
What number does Java start counting String and Array indexes with?
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0
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What is the difference between "Hello" and new String("Hello")?
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Using a string literal adds the string to the string pool. Using the new keyword creates an object that goes on the heap.
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What happens if a string and a number are added together?
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The number will be converted into a string and the two strings will be concatenated
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What does it mean for an object to be immutable?
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Once the object is created it cannot be altered directly.
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True or False: A constructed string and a string in the string pool with the same characters in sequence will return equal when compared with ==
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FALSE. They are different strings in the pool and == checks reference equality
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True or False: A constructed string and a string in the string pool with the same characters in sequence will return equal when compared with the equals() method
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TRUE. String implements the equals method and uses it to compare the actual contents of a string.
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If strings are immutable, how do you change the value of a string variable?
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Assign the results of a string modifying method to the variable.
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What does String.length() do?
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Returns the number of characters in the string as an int
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What does String.charAt() do?
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Returns the character at the specified index
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If indexOf doesn't find any characters in the string that match the provided parameter, what value is returned?
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-1
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True or False: The character at the index specified by the first parameter of a substring is included in the results
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TRUE
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True or False: The character at the index specified by the second parameter of substring is included in the results
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FALSE, it stops before the character at the end index
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True or False: The end index parameter in a substring can be one greater than the actual max index
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TRUE
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If an ending index is not provided, what will substring return?
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A string starting with the provided start index to the end of the string
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What is the difference between the String and StringBuilder classes?
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String is immutable, while StringBuilder is not
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If a class hasn't implemented equals(), how does the method work?
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Uses the default == operator, which checks for reference equality
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What value will a binarySearch on an unsorted array return?
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The value is unpredictable and not useful
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What value will a binarySearch on a sorted array return if the target element is in the array?
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The index of the match
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What value will a binarySearch on a sorted array return if the target element is NOT in the array?
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The negative value where the target element would be minus 1
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True or False: An array can change size after it is instantiated.
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FALSE. An array's size is fixed once it is instantiated. An ArrayList however dynamically changes size as items are added.
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How do you create an ArrayList with a specified type?
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Using generics, which is declared with the diamond: operator <>
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How do you convert an ArrayList to an Array?
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toArray()
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How do you convert an Array to an ArrayList?
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Arrays.asLIst(arrayParameter)
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What is Autoboxing?
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Autoboxing is when Java automatically converts a primitive into the relevant wrapper class so it can be used by processes that require an object over a primitive
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What is a Wrapper Class?
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A Wrapper Class is a class that is the object form of a primitive data type
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When used on a string, what is the difference between parse and valueOf?
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Parse will convert the string into a primitive data type, while valueOf will convert the string into a wrapper class object
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How do you sort an Array?
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Arrays.sort()
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How do you sort an ArrayList?
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Collections.sort()
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How do you create a date/time object with the new LocalDate/Time classes?
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Use the static method of()
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True or False: The month index begins at 1 instead of 0.
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TRUE
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True or False: You can still create a date object with LocalDate/Time with the new keyword
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FALSE, all constructors are private and can only be accessed through the of() static method
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True or False: The LocalDate/Time classes are immutable
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TRUE, results of any methods which modify a date/time object must have their results assigned to a variable
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True or False: Period class instantiators cannot be chained because the methods are static.
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TRUE
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What are the 5 ways a Period object can be instantiated?
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ofYears, ofMonths, ofWeeks, ofDays, and of(Years, Months, Days)
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What is the Time equivalent of a Period?
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Duration
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True or False: You cannot apply a date modifier to a time only object.
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TRUE
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