Java Reference
In-Depth Information
Function substring
For s a string, the call s.substring(h,k) yields the value s[h..k - 1] .
Yes, that is right; character s[k] is not included in the substring s.substring
[h,k] . Arguments h and k must satisfy:
h is the index of some character of s : 0 ≤ h < s.length() .
k satisfies: h ≤ k ≤ s.length() .
Note: s.substring(h,h) denotes the empty string of s beginning at index h .
Equality of strings
When testing for equality, the important thing to remember is that a String
value is an object. Consider String variables s and t as shown here:
s 6
t 7
The expression s==t yields false , even though folders a6 and a7 contain the
same value because expression s==t compares the values in s and t , which are
different. To compare the contents of folders, use instance function equals :
s.equals(t) or t.equals(s)
Both calls shown above yield true . Here is a call that would yield false :
Other methods of class String
Class String has several instance functions and one static function. We list
function calls to some of them below, with brief explanations. Look at the API
specs for String for more explanation. Below, p and q are String s.
p.compareTo(s): = -1 , 0 , or 1 depending on whether p< , = , or >s
p.endsWith(s): = s is a suffix of p
p.indexOf(s): = index of first occurrence of s in p ( -1 if none)
p.lastIndexOf(s): = index of last occurrence of s in p ( -1 if none)
p.startsWith(s): = s is a prefix of p
p.toLowerCase(): = copy of p with all letters in upper case
p.toUpperCase(): = copy of p with all letters in lower case
p.trim(): = copy of p with blanks at the start and end removed
String.valueOf(x): = x represented as a String . x can be any type
Lesson 5-3
goes into more
detail in ex-
plaining these
Changing a name format
Suppose string p contains a name in the format “last-name , first-name”, with
exactly one blank after the comma. The letters may be in upper or lower case.
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