Strings and Characters, Errors and Debugging

String index

The numbered position of a character. the first character is at index 0

.length()

returns the number of characters in a String

.charAt(index)

returns the character at the specified index

.substring(start)

returns the part of a String beginning at start and continuing at the end

.substring(start, end)

returns characters beginning at start and stopping before end

.equals()

compares the contents of two Strings

String comparision

Use .equal() to check whether two Strings contain the same characters

ASCII

A system that represents characters using numeric values

Character and ASCII relationship

each character is connected to a number, allowing characters to be compared or used in calculations

valid String indexes

The indexes go from 0 through length() - 1

Last character

found using s.charAt(s.length() - 1)

Empty string

A String containing no characters ""

Syntax error

code that violates Java's rules and cannot compile

logical error

code that compiles and runs but produces the wrong result

debugging

finding and correcting errors in code

compile-time error

an error discovered when the compiler attempts to translate the source code

Tracing for debugging

following code one statement at a time while recording variable values and output

off by one error

using an index or loop boundary that is one position too high or too low

String index error

trying to use an index outside 0 through length() -1