Answer Posted / rama krishna dwadasi
There are 8 wrapper classes which are equivalent to 8
primitive data types.
Primitive type Wrapper Class
1. byte Byte
2. short Short
3. int Integer
4. long Long
5. float Float
6. double Double
7. char Character
8. boolean Boolean
Wrapper classes are useful in the following ways:-
1. Wrapper classes are used to convert one data type to
another data type. For example:- converting int to double,
double to float, float to String, String to float etc.
2. We can convert primitive to objects and objects to
primitive. For example:- In collections we cannot store
primitive values and we have to store only objects.
Note: All primitive types can be converted to String and
corresponding Wrapper objects.
Following are the general conversions we generally do.
1. primitive to wrapper. (int to Integer).
2. one primitive to another primitive type.(int to float).
3. primitive to String. (int to String).
4. wrapper to primitive.(Integer to int)
5. wrapper to String.(Integer to String)
6. String to primitive.(String to int)
7. String to wrapper.(String to Integer)
1Q: How to convert primitives to wrapper objects?
A: 1) By using the corresponding constructor.
2) By using valueOf(primitive type) method
//Program to convert primitive to wrapper object
// 1) By using constructor
//2) By using valueOf() method
// to convert to int to wrapper object
int i = 10;
Integer x = new Integer(i);
Integer p = Integer.valueOf(i);
//to convert double to wrapper object
double d = 99.99;
Double y = new Double(d);
Double q = Double.valueOf(d);
//to convert boolean to wrapper object
boolean b = true;
Boolean z = new Boolean(b);
Boolean r = Boolean.valueOf(b);
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