Standard Java Classes

Section 3.1 Standard Java Classes

As with any established language, there is a large set of functionality provided by the language via its standard library. This is especially true for Java. We will focus for now solely on a small part of that library, namely some of the key collection classes that are part of the java.util

docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/package-summary.html

package.

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In particular, we will take a closer look at the List and Map interfaces and their standard implementations.

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We will discuss the importance of the difference between interface and implementation at a later time.

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For now, just keep in mind the different use cases for these two important classes:

Lists are used for a collection of items that are in some order, and will typically be iterated over in a loop.

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Maps are used to store key-value pairs, where the most common operation is to find or update the value associated with a particular key.

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Checkpoint 3.1.1.

Look at the List documentation (follow the java.util link above, then scroll and click on the List). Match each of the following list functions with the appropriate description of what they do.

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clear
Removes all the elements from the list
get
Returns the element at a given index
indexOf
Returns the location of first occurrence of an element, if it exists in the list
remove
Removes a specific element from the list
set
Replaces the element at a specific location in the list
add
Adds an element to the end of the list
contains
Determines if the list contains an element

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Checkpoint 3.1.2.

Look at the Map documentation (follow the java.util link above, then scroll and click on the Map). Match each of the following map functions with the appropriate description of what they do.

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clear
Removes all the key-value pairs from the map
keySet
Returns a set of all the keys
get
Returns the value corresponding to a given key
containsKey
Determines if there is a key-value entry with a given key
merge
Sets a value for a key if it didn’t have one already
put
Associates a key to a value
size
Returns the number of key-value pairs in the map
replace
Sets a new value to a key, if there was already a key-value pair for such key

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