How to Concatenate Strings in Java

This example shows how to concatenate strings i.e. how to join them together:

andrew@UBUNTU:~/Java$ cat prog38.java
public class prog38
{
public static void main (String args[])
  {
  String first_name = "Andrew";
  String surname = "Reid";
  String full_name = first_name + " " + surname;
  System.out.println ("full_name = " + full_name);
  }
}
andrew@UBUNTU:~/Java$ javac prog38.java
andrew@UBUNTU:~/Java$ java prog38
full_name = Andrew Reid
andrew@UBUNTU:~/Java$

How to Use Octal Values in Java

You can tell Java that a number is in octal (base 8) by prefixing it with a zero.

In the example below, the variable octal_77 is assigned the value 077 i.e. octal 77. The program then displays the value in decimal (base 10).

UNIX > cat prog21.java

public class prog21

{

public static void main (String args[])

  {

  int octal_77 = 077;

  System.out.println

  ("octal 77 = " + octal_77);

  }

}

UNIX > javac prog21.java

UNIX > java prog21

octal 77 = 63

UNIX > 

You can check the result yourself by converting octal 77 to decimal (base 10) like this:

octal 77 = (in decimal or base 10) (7 x 8) + 7 = 63

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How to Copy a long Java Variable Into an int

You might think that you could copy a long variable into an int variable like this:

 

Solaris > cat prog10.java

public class prog10

{

public static void main (String args[])

  {

  int a;

  long b = 100;

  a = b;

  System.out.println ("a = " + a);

  System.out.println ("b = " + b);

  }

}

Solaris >

 

… but you get a compilation error if you try:

 

Solaris > javac prog10.java

prog10.java:7: possible loss of precision

found   : long

required: int

  a = b;

      ^

1 error

Solaris >

 

You have to do it like this instead:

 

Solaris > cat prog11.java

public class prog11

{

public static void main (String args[])

  {

  int a;

  long b = 100;

  a = (int) b;

  System.out.println ("a = " + a);

  System.out.println ("b = " + b);

  }

}

Solaris > javac prog11.java

Solaris > java prog11

a = 100

b = 100

Solaris >

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