Expression, Statement And Code Blocks In JAVA

In this article we will talk about expressions, statements and code blocks in JAVA.

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What Is Expressions in JAVA & Definition:

Expressions are building blocks off all JAVA programs which are made up of variables, operators, and method invocations. The expression are created according to the syntax and evaluates to a single value. For example, if we want to covert miles to kilometre we first need to know a mile is equal to 1.609344km. Now lets suppose we want to convert 50 miles to kilometres.

double kilometres = (50 * 1.609344);

In the above statement kilometres = (50 * 1.609344) is an expression and data type double is not part of an expression. Typically except data type and ; forms an expression.

Expression Examples In JAVA:

Some more examples of expression:

int score = 50;  //In bold is an expression

If you are using literal value, then except data type and ; is a part of expression. So score = 50 is an expression.

Another example of expression:

if(score == 50){
System.out.println( “This is also an expression” );
}

If you are using control flow if statements, then component inside bracket is a part of expression. So score == 50 is an expression. Remember here braces ( and ) is not part of expression.

Also for methods component inside bracket is a part of expression. So “This is also an expression” is an expression. Remember here also braces ( and ) is not part of expression.

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Statement In JAVA:

Statement forms a complete unit of execution. All statements are terminated with semicolon (;). For example:

int myRoll = 3;

The above complete line is a statement. In JAVA following types form expressions of assignment: any use of ++ or – – , method invocations and object creation expressions can be made into statement by terminating with semicolon(;);

Lets see each type expression made into statement:

Assignment expression made into expression:

int myRoll = 3;

Any use of ++ or — made into expression:

myRoll++;
myRoll--;

Method invocations:

System.out.println(myRoll);
Object creation expressions made into statements
Bike myBike = new Bike();

Important Note: Declaration statements and control flow statements are other two types of statements in JAVA.

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Blocks:

A blocks in JAVA is a group of zero or more statements enclosed between braces. The block begins with opening braces ({) and ends with closing braces (}). Even though it is a statement but doesn’t end with semicolon(;). For example:

{
int myRoll = 3;
String myName = “Abhishek”;
}

It is mostly used with control flow statement. For example:

If (x == 50){
System.out.println(“Example of control flow statement”);
x--;
}

In the above example all code inside braces {} is part of blocks.