Basic instructions

Introduction

Comments

Single line

// This line is fully commented
// This comment looks the same in Java and Pascal
// Writeln('This line is commented out in Pascal');
// System.out.println("This line is commented out in Java");

Multiline

/*
 *  Here is multiline comment
 *  This is in Java
 */

{
 *  Here is multiline comment
 *  This is in Delphi
}

Javadoc comment [Java only]

/**
  * Sets the currency used by this number format when formatting
  * currency values. This does not update the minimum or maximum
  * number of fraction digits used by the number format.
  * <p>
  * The default implementation throws
  * <code>UnsupportedOperationException</code>.
  *
  * @param currency the new currency to be used by this number format
  * @exception UnsupportedOperationException if the number format class
  * doesn't implement currency formatting
  * @exception NullPointerException if <code>currency</code> is null
  * @since 1.4
  */
  public void setCurrency(Currency currency)

Assignment

i := 7;
object := Edit1;
isEqual := true;
object := TObject.Create;

i = 7;
object = Edit1;
isEqual = true;
object = new Object();

Comparison and if

Begin
  If ParamCount <> 2 then begin
    Writeln('Run program with two parameters');
  End else begin
    Writeln(ParamStr(1) = ParamStr(2));
  End;
End.

public class TestCompare1 {
  public static void main(String[] args){
    if (args.length < 2)
      System.out.println("Run program with two parameters");
    else
      System.out.println(args[0] == args[1]);
  }
}

public class TestCompare2 {
  public static void main(String[] args){
    if (args.length < 2)
      System.out.println("Run program with two parameters");
    else
      System.out.println(args[0].equals(args[1]));
  }
}

public class TestCompare3 {
  public static void main(String[] args) {
    String s1 = "STRING";
    String s2 = "STRING";
    System.out.println(s1 == s2);
  }
}

if condition then   
  instruction;

if condition then   
  instruction
else
  instruction;

if (condition)   
  instruction;

if (condition)
  instruction;
else
  instruction;

If  k = 0 then   
  k := 1
else
  k := 0;

if  (k == 0)   
  k = 1;
else
  k = 0;

If k = 0 then begin   
  k := 1
end else begin
  k := 0;
end;

if (k ==  0) {
  k = 1;
} else {
  k = 0;
}

Loops

• For
• While
• Repeat (or similar)

For

for variable_counter := start to expresion do instruction;
for variable_counter := start downto expresion do instruction;

for (variable_counter = start; variable_counter <= expresion; variable_counter++)
  instruction;

for (variable_counter = start; variable_counter >= expresion; variable_counter--)
  instruction;

Program ForTest;
{$APPTYPE CONSOLE}
function loop : integer;
begin
  Writeln('Loop');
  Result := 10;
end;

Var
  I : integer;
Begin
  For i := 1 to loop do
    Writeln(i);
end.

public class ForTest {
  public static void main(String[] args) {
    for (int i = 1; i <= loop(); i++) 
      System.out.println(i);
  }

  public static int loop() {
    System.out.println("Loop");
    return 10;
  }
}

Loop
1
2
3
4
5
6
7
8
9
10

Loop
0
Loop
1
Loop
2
Loop
3
Loop
4
Loop
5
Loop
6
Loop
7
Loop
8
Loop
9
Loop

So remember - when you are porting for loop check your final expression as it will be evaluated only once in Delphi but in every iteration in Java.

for (int i = 0; i < 10; i++)
  System.out.println(i);

While

while condition do   
  instruction;

while (condition)
  instruction;

Var
  K : integer;
Begin
  K := 10;
  While K > 0 do begin
    Writeln(K);
    Dec(K);
  End;
End;

int k = 10;
while (k > 0) {
  System.out.println(k);
  k--;
}

Repeat

Repeat
  Instructions;
Until condition;  

do {
  instructions;
} while (!condition);

Case statement

case selectorExpression of    
  caseList1: statement1;
  ...			
  caseListn: statementn;
else
  statement;
end;

switch (selectorExpression) {
  case caseList1Item1:
  case caseList1Item2: statement1;
    break;
  ...
  case ListnItem: statementn;
    break;
  default: statement;
}

Var
  K,M : integer;
Begin		
  ...  	
  case k of
    1 : Writeln(M*M);
    2 : Writeln(1 / M);
    3 : Writeln(M + M);
  else			
    Writeln(M);	
  End;			
End;

int k;
int m;
...
switch (k) {
  case 1: System.out.println(m*m);
    break;
  case 2: System.out.println(1 / m);
    break;
  case 3: System.out.println(m + m);
    break;
  default:
    System.out.println(m);
}	

case 1: System.out.println(m*m);
case 2: System.out.println(1 / m);
  break;

<m>*<m>
1 / <m>

Var
  C : char;
Begin
...
case c of
'0'..'9' : writeln('Digit');
...
end;

switch (c) {
  case '0':
  case '1':
  case '2':
  case '3':
  case '4':
  case '5':
  case '6':
  case '7':
  case '8':
  case '9': System.out.println("Digit");
    break;
  ...
}

Goto and jumps

With