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(base) MAC:Mon Oct 11:14:07:~&gt; jshell
|  Welcome to JShell -- Version 15.0.1
|  For an introduction type: /help intro

jshell&gt; //What is a generic class

jshell&gt; ArrayList&lt;String&gt; al = new ArrayList&lt;&gt;();
al ==&gt; []

jshell&gt; al.add("hello");
$2 ==&gt; true

jshell&gt; al.add("goodbye");
$3 ==&gt; true

jshell&gt; Integer i = 3;
i ==&gt; 3

jshell&gt; i.getClass()
$5 ==&gt; class java.lang.Integer

jshell&gt; i++;
$6 ==&gt; 3

jshell&gt; i
i ==&gt; 4

jshell&gt; //autoboxing:  Integer i = 3;

jshell&gt; int t = i;
t ==&gt; 4

jshell&gt; //autounboxing

jshell&gt; new Integer(5)
$9 ==&gt; 5

jshell&gt; //calls to new in the wrapper types are tacit.

jshell&gt; Integer.max(3,4)
$10 ==&gt; 4

jshell&gt; Integer.max(3,4,5)
|  Error:
|  method max in class java.lang.Integer cannot be applied to given types;
|    required: int,int
|    found:    int,int,int
|    reason: actual and formal argument lists differ in length
|  Integer.max(3,4,5)
|  ^---------^

jshell&gt; Integer.toString(42)
$11 ==&gt; "42"

jshell&gt; Integer.parseInt("323")
$12 ==&gt; 323

jshell&gt; Integer.parseInt("101110111", 2)
$13 ==&gt; 375

jshell&gt; Integer.parseInt("101110111", 3)
$14 ==&gt; 7627

jshell&gt; Integer.parseInt("101110111", 16)
|  Exception java.lang.NumberFormatException: For input string: "101110111" under radix 16
|        at NumberFormatException.forInputString (NumberFormatException.java:68)
|        at Integer.parseInt (Integer.java:652)
|        at (#15:1)

jshell&gt; Integer.parseInt("10111", 16)
$16 ==&gt; 65809

jshell&gt; new ArrayList&lt;String&gt;()
$17 ==&gt; []

jshell&gt; StringBuffer sb = new StringBuffer();
sb ==&gt; 

jshell&gt; sb.append("cows")
$19 ==&gt; cows

jshell&gt; sb.append("horses")
$20 ==&gt; cowshorses

jshell&gt; sb.append(42)
$21 ==&gt; cowshorses42

jshell&gt; sb.toString()
$22 ==&gt; "cowshorses42"

jshell&gt; //how do I clear a string buffer?

jshell&gt; sb.delete(0, sb.length())
$23 ==&gt; 

jshell&gt; sb
sb ==&gt; 

jshell&gt; for(char k = 'a'; k &lt;= 'z'; k++){sb.append(k);}

jshell&gt; sb
sb ==&gt; abcdefghijklmnopqrstuvwxyz

jshell&gt;