Quote:
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Originally Posted by yjy0079
how do you convert string to integer?
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First of all you need to be precise about terminology. It's important:
In java, there is a
String class (giving rise to String objects). It's
String, not
string.
Now, an
int is a Java primitive (suitable for easy integer calculations), but an
Integer is a class (giving rise to Integer objects---suitable for lots of things). Integer objects, are immutable. The value of an Integer object is determined when the object is created, and can not be changed (You can use the int value of an Integer in an expression to create a new Integer, but you can't change an Integer object itself.)
So: Do you want to convert a Java String to an int primitive or to a Integer object? How are you going to use the result of the conversion?
Some examples:
JAVA Code:
//
// StringToInt.java
//
public class StringToInt {
//public static void main(String[] args) {
public static void main(String[] args) {
// Here is a way to create a String object and set its value.
//
String aString = "42";
//
// A: Two ways to convert a Java String object to a Java Integer object
//
// 1: Use the constructor for a Java Integer object
//
Integer iInt=new Integer(aString);
System.out.println("1: iInt = " + iInt);
// 2: Use the valueOf method of the Integer class.
//
Integer iiInt = Integer.valueOf(aString);
System.out.println("2: iiInt = " + iiInt);
// The following will ***NOT*** work!
// iiInt = iiInt + 1;
//
// Here is one way to effectively increment the int value of an Integer object
//
iiInt = new Integer(iiInt.intValue() + 1);
System.out.println("3: iiInt = " + iiInt + '\n');
//
// B: Two ways to convert a Java String object to an int
//
// 1: Use parseInt
//
int i = Integer.parseInt(aString);
System.out.println("4: i = " + i);
// 2: Get the Integer value of the string, and convert
// to an int with intValue() method of the java Integer class
//
int ii = Integer.valueOf(aString).intValue();
System.out.println("5: ii = " + ii);
//
// It's easy to increment an int
// You could also write
// ++ii;
// or
// ii++;
ii = ii + 1;
System.out.println("6: ii = " + ii);
}
}
Output:
Code:
1: iInt = 42
2: iiInt = 42
3: iiInt = 43
4: i = 42
5: ii = 42
6: ii = 43
Regards,
Dave
29-Oct-2009, 08:00
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