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Statements
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Chapter 2

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Conditional: if-else
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Flow Control

Java vs C/C++
JVM Instructions 1

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A statement is essentially any complete sentence that causes some action to occur. It can encompass multiple operators and operands, as well as multiple sub-statements.

For example, the statement

    int x = 1;

declares a variable x and then assigns the value 1 to it.

This statement

   x = 5.3 *(4.1 / Math.cos (0.2*y));

consists of several expressions - multiplication, division, a method call to a math function - but is still considered a single statement.

Note: A group of statements enclosed in parentheses - called a code block - acts as a single statement. The basic if statement, see below, executes a statement if the test is true, as in

   if (a < b) statement ;

where statement is executed if a is less than b. However, it could also execute a whole block of code as in

   if (a < b) {
      statement 1;
      statement 2;
        ...

   }

where all the statements within the parentheses will execute if a is less than b. Note that a semi-colon is not used after the right parenthesis.

Basic Statements

We list below several important kinds of statements. Some of these are discussed in more detail in the Chapter 2: Java Supplements.

  • Declarations
    Statements that create identifiers, or variable names, for primitive type values and object references. Java is a strongly typed language so every variable must be declared of a particular type. An initializer in the declaration can assign a value to the variable:

        
    int x;
        int x, y; <- multiple declaration
        double y=1.0; <- Declaration & initializer
        double x=5.0, y;


  • Conditional if-else Statement:

        if (i > 10) {
            j++:
        } else {
            j=0;
        }


  • Repetitive Loop Statements:

      for loop

        
    for (i = 0; i < 10; i++) j++;

      while loops

        while (i < 5) {
           i = a.doSomething ();
        }


      do/while loops

        do{
           i = a.doSomething ();
        } while (i < 5)


        Enhanced for loop (added with Java 5.0)

        
    for (type value : container) statement

        where container a Java object, such as an array (see Chatper 3) that contains other objects.
        The statement goes as
    read "for each value in container, do the statement.". We will return
        to this statement in Chapter 10.


  • Other Flow statements:

      
    break statement & statement labels

        while (i < 5) {
           i = a.doSomething ();
           if (i < 0) break; // jump out of the loop
        }

      continue statement

        jmp0: while (b.func()){
          for (int i = 0; i < 4; i++){
            if (a.func ())
    continue jmp0; // jump to start of outer loop
          }
        }


      switch statement

        switch (i) {
            case 1: b.func ();
            case 2: a.func ();
            default: c:func ();
        }


  • Invoking a method (Java version of a subroutine. Methods discussed later):

        Math.sin (0.3);

            Tech
Arithmetic Ops
Math Class
More on Integers
FP : Overview
FP : Java  
  
Demo 1
More Mix/Cast
  Demo 2
Exercises

           Physics
Differential Eq.
Euler Method
  
Demo 1
Predictor-Corrector
  
Demo 2
Exercises

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