First Java Program

Edit/Compile/Execute Cycle

Edit the program and save it with a ".java" extension.

Compile the program creating a file with a ".class" extension.

Execute the program using the "java virtual machine (jvm)"

The Today Program

/**
 * Today program that prints a quote
 *
 * @author Suzanne Balik, 10 Aug 2003
 */ 
public class Today {

  public static void main (String[] args) {
 
    System.out.println("Today is the first day of the rest of your life.");
 
    // This is a comment.
    
    /* Here is another type of comment
       that can span one or
       more lines */
  }
}

Compiling and executing the program:

csc% javac Today.java
csc% java Today
Today is the first day of the rest of your life.

Use the "string concatenation operator", '+', to break up long Strings :


public class Today {

  public static void main (String[] args) {
 
    System.out.println("Today is the first day " +
                       "of the rest of your life.");
  }
}

Use "System.out.print" to break up long Strings:


public class Today {

  public static void main (String[] args) {
 
    System.out.print("Today is the first day ");
    System.out.println("of the rest of your life.");
  }
}

Compile Time or Syntax Errors


public class Today {

  public static void main (String[] args) {
    
    System.out.print("Today is the first day ")
    System.out.println("of the rest of your life.);
    
  }
}

csc% javac Today.java
Today.java:5: ';' expected
    System.out.print("Today is the first day ")
                                               ^
Today.java:6: unclosed string literal
    System.out.println("of the rest of your life.);

Runtime Errors


public class Today {
  
  public static void MAIN (String[] args) {
 
    System.out.print("Today is the first day ");
    System.out.println("of the rest of your life.");

  
  }
}

csc% javac Today.java
csc% java Today
Exception in thread "main" java.lang.NoSuchMethodError: main






public class Zero {

  public static void main(String[] args) {
  
    System.out.println( 24 / 0);
  }
}

csc% javac Zero.java
csc% java Zero
Exception in thread "main" java.lang.ArithmeticException: / by zero
	at Zero.main(Zero.java:5)

Logic Errors


public class Today {

  public static void main (String[] args) {
    
    System.out.println("Toy is the fit day of the rest of yor life.");
 
  }
}

csc% javac Today.java
csc% java Today
Toy is the fit day of the rest of yor life.





public class Average {

  public static void main (String[] args) {
 
    System.out.println("Average: " + ( 3 + 4 + 1 + 4) / 3 );
    
  }
}

csc% javac Average.java
csc% java Average
Average: 4

First Java Program

Edit/Compile/Execute Cycle

Edit the program and save it with a ".java" extension. Compile the program creating a file with a ".class" extension. Execute the program using the "java virtual machine (jvm)"

The Today Program

Compiling and executing the program:

csc% javac Today.java csc% java Today Today is the first day of the rest of your life.

Use the "string concatenation operator", '+', to break up long Strings :

public class Today { public static void main (String[] args) { System.out.println("Today is the first day " + "of the rest of your life."); } }

Use "System.out.print" to break up long Strings:

public class Today { public static void main (String[] args) { System.out.print("Today is the first day "); System.out.println("of the rest of your life."); } } Compile Time or Syntax Errors

Compile Time or Syntax Errors

Runtime Errors

Logic Errors

Edit the program and save it with a ".java" extension.

Compile the program creating a file with a ".class" extension.

Execute the program using the "java virtual machine (jvm)"

public class Today { public static void main (String[] args) { System.out.print("Today is the first day "); System.out.println("of the rest of your life."); } }

Compile Time or Syntax Errors