© 2001 by Ashby M. Woolf Revision 3 Using Java Operators The Basic Toolkit Pliers, Screwdriver, Hammer and Drill

© 2001 by Ashby M. Woolf Revision 3 Assignment Operator (=) lvalue = rvalue; Take the value of the rvalue and store it in the lvalue. The rvalue is any constant, variable or expression. The lvalue is named variable. w = 10; x = w; z = (x - 2)/(2 + 2);

© 2001 by Ashby M. Woolf Revision 3 Mathematical Operators Addition + Subtraction - Multiplication * Division/ Modulus%

© 2001 by Ashby M. Woolf Revision 3 Simple Arithmetic public class Example { public static void main(String[] args) { int j, k, p, q, r, s, t; j = 5; k = 2; p = j + k; q = j - k; r = j * k; s = j / k; t = j % k; System.out.println("p = " + p); System.out.println("q = " + q); System.out.println("r = " + r); System.out.println("s = " + s); System.out.println("t = " + t); } > java Example p = 7 q = 3 r = 10 s = 2 t = 1 >

© 2001 by Ashby M. Woolf Revision 3 Shorthand Operators +=, -=, *=, /=, %= Common Shorthand a = a + b;a += b; a = a - b;a -= b; a = a * b;a *= b; a = a / b;a /= b; a = a % b;a %= b;

© 2001 by Ashby M. Woolf Revision 3 Shorthand Operators public class Example { public static void main(String[] args) { int j, p, q, r, s, t; j = 5; p = 1; q = 2; r = 3; s = 4; t = 5; p += j; q -= j; r *= j; s /= j; t %= j; System.out.println("p = " + p); System.out.println("q = " + q); System.out.println("r = " + r); System.out.println("s = " + s); System.out.println("t = " + t); } > java Example p = 6 q = -3 r = 15 s = 0 t = 0 >

© 2001 by Ashby M. Woolf Revision 3 Shorthand Increment and Decrement ++ and -- Common Shorthand a = a + 1;a++; or ++a; a = a - 1;a--; or --a;

© 2001 by Ashby M. Woolf Revision 3 Increment and Decrement > java example p = 6 q = 6 j = 7 r = 6 s = 6 > public class Example { public static void main(String[] args) { int j, p, q, r, s; j = 5; p = ++j; // j = j + 1; p = j; System.out.println("p = " + p); q = j++; // q = j; j = j + 1; System.out.println("q = " + q); System.out.println("j = " + j); r = --j; // j = j -1; r = j; System.out.println("r = " + r); s = j--; // s = j; j = j - 1; System.out.println("s = " + s); }

© 2001 by Ashby M. Woolf Revision 3 Arithmetic Operators A Change of Topic Casting long 64 bit l int 32 bit i

© 2001 by Ashby M. Woolf Revision 3 long 64 bit int 32 bit l i int i; i = (int)l; l = (long)i; Moving Between Buckets "Casting" long l; l = i; long 64 bit int 32 bit l i Widening Narrowing

© 2001 by Ashby M. Woolf Revision 3 DeclarationSize and TypeNumber Range byte b;// 8 bit integer to short s;// 16 bit integer to char c;// 16 bit Unicode 0 to int i;// 32 bit integer to long l;// 64 bit integer to float f;// 32 bit floating pointIEEE754 Standard double d;// 64 bit floating pointIEEE754 Standard The Primitive Numbers

© 2001 by Ashby M. Woolf Revision 3 Casting the Primitives b = (byte)s; b = (byte)c; b = (byte)i; b = (byte)l; b = (byte)f; b = (byte)d; i = (int)b; i = (int)s; i = (int)c; i = (int)l; i = (int)f; i = (int)d; l = (long)b; l = (long)s; l = (long)c; l = (long)i; l = (long)f; l = (long)d; s = (short)b; s = (short)c; s = (short)i; s = (short)l; s = (short)f; s = (short)d; 2's Complement c = (char)b; c = (char)s; c = (char)i; c = (char)l; c = (char)f; c = (char)d; Positive Only f = (float)b; f = (float)s; f = (float)c; f = (float)i; f = (float)l; f = (float)d; d = (double)b; d = (double)s; d = (double)c; d = (double)i; d = (double)l; d = (double)f; Floating Point b = (byte)s; b = (byte)c; b = (byte)i; b = (byte)l; b = (byte)f; b = (byte)d; i = b; i = s; i = c; i = (int)l; i = (int)f; i = (int)d; l = b; l = s; l = c; l = i; l = (long)f; l = (long)d; s = b; s = (short)c; s = (short)i; s = (short)l; s = (short)f; s = (short)d; 2's Complement c = (char)b; c = (char)s; c = (char)i; c = (char)l; c = (char)f; c = (char)d; Positive Only f = b; f = s; f = c; f = i; f = l; f = (float)d; d = b; d = s; d = c; d = i; d = l; d = f; Floating Point

© 2001 by Ashby M. Woolf Revision 3 Acceptable Implicit Casts char 16 bit double 64 bit float 32 bit long 64 bit int 32 bit short 16 bit byte 8 bit Illegal b = l; l = f; c = s; OK l = b; i = c; f = l

© 2001 by Ashby M. Woolf Revision 3 char 16 bit double 64 bit float 32 bit long 64 bit int 32 bit short 16 bit byte 8 bit char 16 bit double 64 bit float 32 bit long 64 bit int 32 bit short 16 bit byte 8 bit Automatic Promotion with Arithmetic Illegal Casts s = s + b; s = s + s; OK s = (short)(s + b); s = (short)(s + s); Arithmetic is never done in 8 or 16 bit containers.

© 2001 by Ashby M. Woolf Revision 3 char 16 bit double 64 bit float 32 bit long 64 bit int 32 bit short 16 bit byte 8 bit Arithmetic Promotion with Mixed Primitives Illegal Casts i = i + l; f = f + d; l = l + f; OK i = (int)(i + l); d = (double)(f + d); l = (long)(l + f); Arithmetic is done in the "widest" type.

© 2001 by Ashby M. Woolf Revision 3 Implicit Casts in Method Calls char 16 bit double 64 bit float 32 bit long 64 bit int 32 bit short 16 bit byte 8 bit Illegal i = st.indexOf(f); OK i = st.indexOf(c); i = st.indexOf(b); For: String st; and, public int indexOf(int ch);

© 2001 by Ashby M. Woolf Revision 3 Casting A Change of Topic The Logical and Relational Operators

© 2001 by Ashby M. Woolf Revision 3 Relational Operators > = <= == != Primitives Greater Than > Less Than < Greater Than or Equal >= Less Than or Equal<= Primitives or Object References Equal (Equivalent)== Not Equal != The Result is Always true or false

© 2001 by Ashby M. Woolf Revision 3 Relational Operator Examples public class Example { public static void main(String[] args) { int p =2; int q = 2; int r = 3; Integer i = new Integer(10); Integer j = new Integer(10); System.out.println("p < r " + (p < r)); System.out.println("p > r " + (p > r)); System.out.println("p == q " + (p == q)); System.out.println("p != q " + (p != q)); System.out.println("i == j " + (i == j)); System.out.println("i != j " + (i != j)); } > java Example p < r true p > r false p == q true p != q false i == j false i != j true >

© 2001 by Ashby M. Woolf Revision 3 Logical Operators (boolean) && || ! Logical AND && Logical OR || Logical NOT !

© 2001 by Ashby M. Woolf Revision 3 Logical (&&) Operator Examples public class Example { public static void main(String[] args) { boolean t = true; boolean f = false; System.out.println("f && f " + (f && f)); System.out.println("f && t " + (f && t)); System.out.println("t && f " + (t && f)); System.out.println("t && t " + (t && t)); } > java Example f && f false f && t false t && f false t && t true >

© 2001 by Ashby M. Woolf Revision 3 Logical (||) Operator Examples public class Example { public static void main(String[] args) { boolean t = true; boolean f = false; System.out.println("f || f " + (f || f)); System.out.println("f || t " + (f || t)); System.out.println("t || f " + (t || f)); System.out.println("t || t " + (t || t)); } > java Example f || f false f || t true t || f true t || t true >

© 2001 by Ashby M. Woolf Revision 3 Logical (!) Operator Examples public class Example { public static void main(String[] args) { boolean t = true; boolean f = false; System.out.println("!f " + !f); System.out.println("!t " + !t); } > java Example !f true !t false >

© 2001 by Ashby M. Woolf Revision 3 Logical Operator Examples Short Circuiting with && public class Example { public static void main(String[] args) { boolean b; int j, k; j = 0; k = 0; b = ( j++ == k ) && ( j == ++k ); System.out.println("b, j, k " + b + ", " + j + ", " + k); j = 0; k = 0; b = ( j++ != k ) && ( j == ++k ); System.out.println("b, j, k " + b + ", " + j + ", " + k); } > java Example b, j, k true 1, 1 > java Example b, j, k true 1, 1 b, j, k false 1, 0 >

© 2001 by Ashby M. Woolf Revision 3 Logical Operator Examples Short Circuiting with || public class Example { public static void main(String[] args) { boolean b; int j, k; j = 0; k = 0; b = ( j++ == k ) || ( j == ++k ); System.out.println("b, j, k " + b + ", " + j + ", " + k); j = 0; k = 0; b = ( j++ != k ) || ( j == ++k ); System.out.println("b, j, k " + b + ", " + j + ", " + k); } > java Example b, j, k true 1, 0 > java Example b, j, k true 1, 0 b, j, k true 1, 1 >

© 2001 by Ashby M. Woolf Revision 3 The Logical and Relational Operators A Change of Topic Manipulating the Bits

© 2001 by Ashby M. Woolf Revision 3 Logical Operators (Bit Level) & | ^ ~ AND & OR | XOR ^ NOT ~

© 2001 by Ashby M. Woolf Revision 3 Twos Complement Numbers Base 10 A byte of binary

© 2001 by Ashby M. Woolf Revision 3 Adding Twos Complements Base 10Binary Base 10Binary

© 2001 by Ashby M. Woolf Revision 3 Logical Operators (Bit Level) & | ^ ~ int a = 10; // = 10 int b = 12; // = 12 a b a & b a b a | b a b a ^ b a ~a & AND | OR ^ XOR ~ NOT

© 2001 by Ashby M. Woolf Revision 3 Logical (bit) Operator Examples public class Example { public static void main(String[] args) { int a = 10; // = 10 int b = 12; // = 12 int and, or, xor, na; and = a & b; // = 8 or = a | b; // = 14 xor = a ^ b; // = 6 na = ~a; // = -11 System.out.println("and " + and); System.out.println("or " + or); System.out.println("xor " + xor); System.out.println("na " + na); } > java Example and 8 or 14 xor 6 na -11 >

© 2001 by Ashby M. Woolf Revision 3 Shift Operators (Bit Level) > >>> Shift Left <<Fill with Zeros Shift Right >>Based on Sign Shift Right >>>Fill with Zeros

© 2001 by Ashby M. Woolf Revision 3 Shift Operators > int a = 3; // = 3 int b = -4; // = -4 a a << b b << << Left >> Right a a >> b b >>

© 2001 by Ashby M. Woolf Revision 3 Shift Operator >>> int a = 3; // = 3 int b = -4; // = -4 >>> Right 0 a a >>> b b >>> big

© 2001 by Ashby M. Woolf Revision 3 Shift Operator Examples public class Example { public static void main(String[] args) { int a = 3; // = 3 int b = -4; // = -4 System.out.println("a<<2 = " + (a<<2)); System.out.println("b<<2 = " + (b<<2)); System.out.println("a>>2 = " + (a>>2)); System.out.println("b>>2 = " + (b>>2)); System.out.println("a>>>2 = " + (a>>>2)); System.out.println("b>>>2 = " + (b>>>2)); } > java Example a<<2 = 12 b<<2 = -16 a>>2 = 0 b>>2 = -1 a>>>2 = 0 b>>>2 = >

© 2001 by Ashby M. Woolf Revision 3 Shift Operator >>> and Automatic Arithmetic Promotion byte a = 3; // = 3 byte b = -4; // = -4 byte c; c = (byte) a >>> 2 c = (byte) b >>> 2 >>> Right Fill 0 a a >>> c = (byte) b b >>> c = (byte) Much to big for byte

© 2001 by Ashby M. Woolf Revision 3 Which Operators Operate On What Operators && || ! Unary * / % > = <= == != > >>> & | ^ ~ = op= etc. floatdouble Floating Point charbyteshortintlong Automatic Promotion Except Automatic Promotion Except Automatic Promotion Except Automatic Promotion Except Automatic Promotion Except Automatic Promotion Except Automatic Promotion Automatic Promotion Automatic Promotion Integral boolean Logical Any Object + with String Only Reference Only Not Content

© 2001 by Ashby M. Woolf Revision 3 Assignment Operator (=) and Classes Date x = new Date(); Date y = new Date(); x = y;

© 2001 by Ashby M. Woolf Revision 3 Assignment Operator (=) and Classes Date x = new Date(); Date y = new Date(); x = y;

© 2001 by Ashby M. Woolf Revision 3 Manipulating the Bits A Change of Topic Some Odds and Ends

© 2001 by Ashby M. Woolf Revision 3 Ternary Operator ? : If true this expression is evaluated and becomes the value entire expression. Any expression that evaluates to a boolean value. If false this expression is evaluated and becomes the value entire expression. boolean_expression ? expression_1 : expression_2

© 2001 by Ashby M. Woolf Revision 3 Ternary ( ? : ) Operator Examples public class Example { public static void main(String[] args) { boolean t = true; boolean f = false; System.out.println("t?true:false "+(t ? true : false )); System.out.println("t?1:2 "+(t ? 1 : 2 )); System.out.println("f?true:false "+(f ? true : false )); System.out.println("f?1:2 "+(f ? 1 : 2 )); } > java Example t?true:false true t?1:2 1 f?true:false false f?1:2 2 >

© 2001 by Ashby M. Woolf Revision 3 String (+) Operator String Concatenation "Now is " + "the time." "Now is the time."

© 2001 by Ashby M. Woolf Revision 3 String (+) Operator Automatic Conversion to a String If either expression_1 If either expression_1 or expression_2 evaluates to a string the other will be converted to a string if needed. The result will be their concatenation. expression_1 + expression_2

© 2001 by Ashby M. Woolf Revision 3 String (+) Operator Automatic Conversion with Primitives "The number is " + 4 "The number is " + "4" "The number is 4"

© 2001 by Ashby M. Woolf Revision 3 String (+) Operator Automatic Conversion with Objects "Today is " + new Date() "Today is " + "Wed 27 22:12;26 CST 2000" "Today is Wed 27 22:12;26 CST 2000" "Today is " + new Date().toString()

© 2001 by Ashby M. Woolf Revision 3 Operator Precedence ! ~ () * / % + - > >>> > = <= instanceof == != & | ^ && || ?: = (and += etc.) Unary Arithmetic Shift Comparison Logical Bit Boolean Ternary Assignment

© 2001 by Ashby M. Woolf Revision 3 Passing Classes to Methods class Letter { char c; } public class PassObject { static void f(Letter y) { y.c = 'z'; } public static void main(String[] args) { Letter x = new Letter(); x.c = 'a'; System.out.println("1: x.c: " + x.c); // Prints 1: x.c: a f(x); System.out.println("2: x.c: " + x.c); // Prints 2: x.c: z }

© 2001 by Ashby M. Woolf Revision 3 Passing Primitives to Methods class Letter { char c; } public class PassPrimitive { static void f(char y) { y = 'z'; } public static void main(String[] args) { Letter x = new Letter(); x.c = 'a'; System.out.println("1: x.c: " + x.c); // Prints 1: x.c: a f(x.c); System.out.println("2: x.c: " + x.c); // Prints 2: x.c: a }

© 2001 by Ashby M. Woolf Revision 3 End of Content