Java Review

The Java API

The Object class methods

• Boolean equals (Object obj)

– Makes shallow comparison to determine equality

• String toString( )

– The method toString is implicitly invoked when an object is an argument of println

String classes

• String class methods

– st.length( ) returns an int

– st.compareTo(str2) returns an int

– st.substring(index1, index2) returns a String

– st.trim( ) returns a String with the leading and trailing blanks removed

– These strings are nonmutable

• StringTokenizer

– Constructors

• One argument-- string to be tokenized

• Two arguments– string plus the delimiters (space is the default)

– strT.nextToken( ) returns the next token

– strT.hasMoreTokens( ) returns a boolean

Standard Java I/O

• Standard output to the screen

– System.out.println(“some string”)

– println differs from print in that it terminates a line of output

• Standard input from the keyboard

– You need an object of type BufferedReader

– Example:

BufferedReader myInput;
myInput = new BufferedReader(new
InputStreamReader(System.in);

String str = myInput.readLine( );

Reading integers

• First create an object of type BufferedReader as in the previous slide to read the int first as a String

BufferedReader br = new BufferedReader(new
InputStreamReader(System.in);

• Then convert it to an int

• int i = Integer.parseInt(br.readLine( ));

• parseInt is a static method of the predefined wrapper class Integer