20.12

java.lang.String

THE PACKAGE JAVA.LANG

20.12.17

public int compareTo(String anotherString)

throws NullPointerException

The character sequence represented by this

String

 object is compared lexico 

graphically to the character sequence represented by the argument string. The

result is a negative integer if this

String

 object lexicographically precedes the

argument string. The result is a positive integer if this

String

 object lexicograph 

ically follows the argument string. The result is zero if the strings are equal;

com 

pareTo

 returns

0

 exactly when the

equals

 method ( 20.12.9) would return

true

.

If

anotherString

 is

null

, then a

NullPointerException

 is thrown.

This is the definition of lexicographic ordering. If two strings are different,

then either they have different characters at some index that is a valid index for

both strings, or their lengths are different, or both. If they have different characters

at one or more index positions, let

k

 be the smallest such index; then the string

whose character at position

k

 has the smaller value, as determined by using the

<

operator, lexicographically precedes the other string. In this case,

compareTo

returns the difference of the two character values at position

k

 in the two strings 

that is, the value:

this.charAt(k) anotherString.charAt(k)

If there is no index position at which they differ, then the shorter string lexico 

graphically precedes the longer string. In this case,

compareTo

 returns the differ 

ence of the lengths of the strings that is, the value:

this.length() anotherString.length()

20.12.18

public boolean regionMatches(int toffset,

String other, int ooffset, int len)

throws NullPointerException

A substring of this

String

 object is compared to a substring of the argument

other

. The result is

true

 if these substrings represent identical character

sequences. The substring of this

String

 object to be compared begins at index

toffset

 and has length

len

. The substring of

other

 to be compared begins at

index

ooffset

 and has length

len

. The result is

false

 if and only if at least one

of the following is true:

toffset

 is negative.

ooffset

 is negative.

toffset+len

 is greater than the length of this

String

 object.

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