module5.lst

Mcgraw-Hill - Java 2 - A Beginner S Guide, 2Nd Ed - 2003 -prog.

    // more errors on smallQ 
    System.out.print("Contents of smallQ: "); 
    for(i=0; i < 5; i++) {  
      ch = smallQ.get(); 
 
      if(ch != (char) 0) System.out.print(ch); 
    } 
  } 
}

listing 13
// Introduce String. 
class StringDemo {  
  public static void main(String args[]) {  
    // declare strings in various ways 
    String str1 = new String("Java strings are objects."); 
    String str2 = "They are constructed various ways."; 
    String str3 = new String(str2); 
 
    System.out.println(str1); 
    System.out.println(str2); 
    System.out.println(str3); 
  }  
}

listing 14
// Some String operations. 
class StrOps {  
  public static void main(String args[]) {  
    String str1 = 
      "When it comes to Web programming, Java is #1.";  
    String str2 = new String(str1); 
    String str3 = "Java strings are powerful.";  
    int result, idx; 
    char ch; 
 
    System.out.println("Length of str1: " +  
                       str1.length());  
  
    // display str1, one char at a time. 
    for(int i=0; i < str1.length(); i++) 
      System.out.print(str1.charAt(i));  
    System.out.println();  
 
    if(str1.equals(str2))  
      System.out.println("str1 == str2");  
    else  
      System.out.println("str1 != str2");  
  
    if(str1.equals(str3))  
      System.out.println("str1 == str3");  
    else  
      System.out.println("str1 != str3");  
 
    result = str1.compareTo(str3); 
    if(result == 0) 
      System.out.println("str1 and str3 are equal"); 
    else if(result < 0) 
      System.out.println("str1 is less than str3"); 
    else 
      System.out.println("str1 is greater than str3"); 
 
 
    // assign a new string to str2 
    str2 = "One Two Three One"; 
 
    idx = str2.indexOf("One"); 
    System.out.println("Index of first occurence of One: " + idx); 
    idx = str2.lastIndexOf("One"); 
    System.out.println("Index of last occurence of One: " + idx); 
     
  }  
}

listing 15
// Demonstrate String arrays.  
class StringArrays {  
  public static void main(String args[]) {  
    String str[] = { "This", "is", "a", "test." };  
  
    System.out.println("Original array: ");  
    for(int i=0; i < str.length; i++) 
      System.out.print(str[i] + " ");  
    System.out.println("\n");  
  
    // change a string  
    str[1] = "was";  
    str[3] = "test, too!";  
  
    System.out.println("Modified array: "); 
    for(int i=0; i < str.length; i++) 
      System.out.print(str[i] + " ");  
  }  
} 

listing 16
// Use substring(). 
class SubStr {  
  public static void main(String args[]) {  
    String orgstr = "Java makes the Web move."; 
 
    // construct a substring 
    String substr = orgstr.substring(5, 18); 
 
     
    System.out.println("orgstr: " + orgstr); 
    System.out.println("substr: " + substr); 
 
  }  
}

listing 17
// Display all command-line information. 
class CLDemo {  
  public static void main(String args[]) { 
    System.out.println("There are " + args.length + 
                       " command-line arguments."); 
 
    System.out.println("They are: "); 
    for(int i=0; i<args.length; i++)  
      System.out.println(args[i]);  
  }  
}

listing 18
// A simple automated telphone directory. 
class Phone {  
  public static void main(String args[]) {  
    String numbers[][] = { 
      { "Tom", "555-3322" }, 
      { "Mary", "555-8976" }, 
      { "Jon", "555-1037" }, 
      { "Rachel", "555-1400" } 
    }; 
    int i; 
 
    if(args.length != 1) 
      System.out.println("Usage: java Phone <name>"); 
    else { 
      for(i=0; i<numbers.length; i++) { 
        if(numbers[i][0].equals(args[0])) { 
          System.out.println(numbers[i][0] + ": " + 
                             numbers[i][1]); 
          break; 
        } 
      } 
      if(i == numbers.length) 
        System.out.println("Name not found."); 
    } 
  }  
}

listing 19
// Uppercase letters. 
class UpCase {  
  public static void main(String args[]) { 
    char ch;  
  
    for(int i=0; i < 10; i++) { 
      ch = (char) ('a' + i);  
      System.out.print(ch); 
 
      // This statement turns off the 6th bit.   
      ch = (char) ((int) ch & 65503); // ch is now uppercase  
  
      System.out.print(ch + " ");  
    } 
  } 
}

listing 20
// Display the bits within a byte.  
class ShowBits { 
  public static void main(String args[]) { 
    int t; 
    byte val;  
  
    val = 123; 
    for(t=128; t > 0; t = t/2) { 
      if((val & t) != 0) System.out.print("1 ");  
      else System.out.print("0 ");  
    } 
  } 
}

listing 21
// Lowercase letters. 
class LowCase {  
  public static void main(String args[]) { 
    char ch;  
  
    for(int i=0; i < 10; i++) { 
      ch = (char) ('A' + i);  
      System.out.print(ch); 
 
      // This statement turns on the 6th bit.   
      ch = (char) ((int) ch | 32); // ch is now lowercase  
  
      System.out.print(ch + " ");  
    } 
  } 
}

listing 22
// Use XOR to encode and decode a message. 
class Encode {  
  public static void main(String args[]) { 
    String msg = "This is a test";  
    String encmsg = ""; 
    String decmsg = ""; 
    int key = 88; 
 
    System.out.print("Original message: "); 
    System.out.println(msg); 
 
    // encode the message 
    for(int i=0; i < msg.length(); i++) 
      encmsg = encmsg + (char) (msg.charAt(i) ^ key); 
 
    System.out.print("Encoded message: "); 
    System.out.println(encmsg); 
 
    // decode the message 
    for(int i=0; i < msg.length(); i++) 
      decmsg = decmsg + (char) (encmsg.charAt(i) ^ key); 
    
    System.out.print("Decoded message: "); 
    System.out.println(decmsg); 
  } 
}

listing 23
// Demonstrate the bitwise NOT. 
class NotDemo { 
  public static void main(String args[]) { 
    byte b = -34; 
 
    for(int t=128; t > 0; t = t/2) { 
      if((b & t) != 0) System.out.print("1 ");  
      else System.out.print("0 ");  
    } 
    System.out.println(); 
 
    // reverse all bits 
    b = (byte) ~b; 
 
    for(int t=128; t > 0; t = t/2) { 
      if((b & t) != 0) System.out.print("1 ");  
      else System.out.print("0 ");  
    } 
  } 
} 

listing 24
// Demonstrate the shift << and >> operators. 
class ShiftDemo { 
  public static void main(String args[]) { 
    int val = 1; 
 
    for(int i = 0; i < 8; i++) {  
      for(int t=128; t > 0; t = t/2) { 
        if((val & t) != 0) System.out.print("1 ");  
        else System.out.print("0 ");  
      } 
      System.out.println(); 
      val = val << 1; // left shift 
    } 
    System.out.println(); 
 
    val = 128; 
    for(int i = 0; i < 8; i++) {  
      for(int t=128; t > 0; t = t/2) { 
        if((val & t) != 0) System.out.print("1 ");  
        else System.out.print("0 ");  
      } 
      System.out.println(); 
      val = val >> 1; // right shift 
    } 
  } 
}

listing 25
/* 
   Project 5-3 
 
   A class that displays the binary representation of a value. 
*/ 
 
class ShowBits { 
  int numbits; 
 
  ShowBits(int n) { 
    numbits = n; 
  } 
 
  void show(long val) { 
    long mask = 1; 
 
    // left-shit a 1 into the proper position 
    mask <<= numbits-1; 
 
    int spacer = 0; 
    for(; mask != 0; mask >>>= 1) { 
      if((val & mask) != 0) System.out.print("1"); 
      else System.out.print("0"); 
      spacer++; 
      if((spacer % 8) == 0) { 
        System.out.print(" "); 
        spacer = 0; 
      } 
    } 
    System.out.println(); 
  } 
} 
 
// Demonstrate ShowBits. 
class ShowBitsDemo { 
  public static void main(String args[]) { 
    ShowBits b = new ShowBits(8); 
    ShowBits i = new ShowBits(32); 
    ShowBits li = new ShowBits(64); 
 
    System.out.println("123 in binary: "); 
    b.show(123); 
 
    System.out.println("\n87987 in binary: "); 
    i.show(87987); 
 
    System.out.println("\n237658768 in binary: "); 
    li.show(237658768); 
 
 
    // you can also show low-order bits of any integer 
    System.out.println("\nLow order 8 bits of 87987 in binary: "); 
    b.show(87987);  
  } 
}

listing 26
// Prevent a division by zero using the ?. 
class NoZeroDiv { 
  public static void main(String args[]) { 
    int result; 
 
    for(int i = -5; i < 6; i++) { 
      result = i != 0 ? 100 / i : 0; 
      if(i != 0)  
        System.out.println("100 / " + i + " is " + result); 
    } 
  } 
} 

listing 27
// Prevent a division by zero using the ?. 
class NoZeroDiv2 { 
  public static void main(String args[]) { 
 
    for(int i = -5; i < 6; i++)  
      if(i != 0 ? true : false)  
        System.out.println("100 / " + i + 
                           " is " + 100 / i); 
  } 
}