Java basic programming structure (2)

(6) String
1. here we need to point out that it is an object rather than a character array.

2. It is immutable, with no append () or reverse ()

3. Use double quotation marks and + for connection

4. provide some common functions. For more information, see the API documentation.
Tostring ();
Int length () -- number of chars
Char charat (INT index) -- char at given 0-based index
Int indexof (char c) -- first occurrence of char, or-1
Int indexof (string S)
Boolean equals (object) -- test if two strings have the same characters
Boolean inclusignorecase (object) -- as abve, but ignoring case
String tolowercase () -- return a new string, lowercase
String substring (INT begin, int end) -- return a new string made of the begin .. end-1 substring from the original

5. Initialization
S1 = new string ("this is some java string ");
S1 = new string ("this is some java string ");

6. Example
String A = "hello"; // allocate 2 string objects
String B = "there ";
String c = A; // point to same string as a-Fine

Int Len = A. Length (); // 5
String d = a + "" + B; // "Hello there"

Int find = D. indexof ("there"); // find: 6
String sub = D. substring (6, 11); // extract: "there"

Sub = B; // false (= compares pointers)
Sub. Equals (B); // true (a "deep" comparison)

String A = "hello"; // allocate 2 string objects
String B = "there ";
String c = A; // point to same string as a-Fine

Int Len = A. Length (); // 5
String d = a + "" + B; // "Hello there"

Int find = D. indexof ("there"); // find: 6
String sub = D. substring (6, 11); // extract: "there"

Sub = B; // false (= compares pointers)

Use the equals method;
S. Equals (t) // returns true if the strings S and T are equal, false otherwise.
S and T can be string variables or string constants. "Hello". Equals (command) // OK
To test if two strings are identical limits t for the Upper/lowercase letter distinction
"Hello". equalsignorecase ("hello ")

7. Generally, = is not used for comparison.
String greeting = "hello ";
If (greeting = "hello")... // probably true
If (greeting. substring (0, 4) = "hell")... // probably false

8. stringbuffer
Different from string,
Append () method-lets you add characters to the end of a stringbuffer object

Insert () method-lets you add characters at a specified location within a stringbuffer object

Setcharat () method-use to alter just one character in a stringbuffer

Example:
Stringbuffer buff = new stringbuffer ();
For (INT I = 0; I <100; I ++ ){
Buff. append (<some thing> );
// Efficient append
}
String result = buff. tostring ();
// Make a string once done with appending

9. stringtokenizer
You can use some tokens to separate strings.
Example:
String teststring = "one-two-three ";
Stringtokenizer ST = new stringtokenizer (teststring ,"-");
While (St. hasmoretokens ()){
String nextname = ST. nexttoken ();
System. Out. println (nextname );
}
Result:
One
Two
Three