MATHEMATICAL FUNCTIONS, CHARACTERS, AND STRINGS - Introduction to Java Programming: Comprehensive Version - page 132

(e.g., a number), the nonstring value is converted into a string and concatenated with the other
string. Here are some examples:

// Three strings are concatenated
String message = "Welcome " + "to " + "Java" ;

// String Chapter is concatenated with number 2
String s = "Chapter" + 2 ; // s becomes Chapter2

// String Supplement is concatenated with character B
String s1 = "Supplement" + 'B' ; // s1 becomes SupplementB

If neither of the operands is a string, the plus sign ( + ) is the addition operator that adds two
numbers.
The augmented += operator can also be used for string concatenation. For example, the
following code appends the string "and Java is fun" with the string "Welcome to
Java" in message .

message += " and Java is fun" ;

So the new message is "Welcome to Java and Java is fun" .
If i = 1 and j = 2 , what is the output of the following statement?

System.out.println( "i + j is " + i + j);

The output is "i + j is 12" because "i + j is " is concatenated with the value of
i first. To force i + j to be executed first, enclose i + j in the parentheses, as follows:

System.out.println( "i + j is " + (i + j));

4.4.4 Converting Strings
The toLowerCase() method returns a new string with all lowercase letters and the
toUpperCase() method returns a new string with all uppercase letters. For example,

"Welcome".toLowerCase() returns a new string welcome .
"Welcome".toUpperCase() returns a new string WELCOME .

toLowerCase()
toUpperCase()

The trim() method returns a new string by eliminating whitespace characters from both
ends of the string. The characters ' ' , \t , \f , \r , or \n are known as whitespace characters .
For example,

whitespace character

"\t Good Night \n".trim() returns a new string Good Night .

trim()

4.4.5 Reading a String from the Console
To read a string from the console, invoke the next() method on a Scanner object. For
example, the following code reads three strings from the keyboard:

read strings

Scanner input = new Scanner(System.in);
System.out.print( "Enter three words separated by spaces: " );
String s1 = input.next();
String s2 = input.next();
String s3 = input.next();
System.out.println( "s1 is " + s1);
System.out.println( "s2 is " + s2);
System.out.println( "s3 is " + s3);