Casting (Type Conversion)

Automatic Conversion

Java performs automatic type conversion when the type of the expression on the right hand side of an assignment operator safely promotes to the type of the variable on the left hand side of the assignment operator. Thus we can safely assign: byte -> short -> int -> long -> float -> double. Symbol (->) used here interprets to "to a".

Lets take an example, 

// 64 bit long integer
long myLongInteger;
// 32 bit standard integer
int myInteger;
myLongInteger = myInteger;

• Upcasting
•  Downcasting

Upcasting

Casting a reference with the class hierarchy in a direction from the sub classes towards the root then this type of casting is termed as upcasting. Upcasting does not require a cast operator.

DownCasting

On the other hand, casting a reference with hierarchal class order in a direction from the root class towards the children or subclasses, then it is known as downcasting.

Explicit Conversion (Casting)

Automatic type casting does work in case of narrowing i.e. when a data type requiring more storage is converted into a data type that requires less storage. E.g. conversion of a long to an int does not perform because the first requires more storage than the second and consequently information may be lost. In such situations an explicit conversion is required. 

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Comments

Vivek
September 11, 2011
Explicit Type Casting in Mixed Expressions

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what is the order of evaluation of this code in java int i ; char c ; double d; (char) d + i/c Would double be converted first to character and then the expression is evaluated or first expression will be evaluated and then convereted to char by (char) Thanks and regards, Vivek

JAYESH SARVAIYA
January 10, 2012
java

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give me always java questions

Chandra Sekar Jittim
February 25, 2012
Type Casting

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What is Type Casting??

ravitheja
June 8, 2012
how would we use conversion java

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Java performs automatic type conversion when the type of the expression on the right hand side of an assignment operator safely promotes to the type of the variable on the left hand side of the assignment operator. Thus we can safely assign: byte -> short -> int -> long -> float -> double. Symbol (->) used here interprets to "to a". Lets take an example, // 64 bit long integer long myLongInteger; // 32 bit standard integer int myInteger; myLongInteger = myInteger; In the above example, extra storage associated with the long integer, simply results in padding with extra zeros.