Java Tutorial/Operators/Logical Operators
Содержание
- 1 AND operator
- 2 Boolean Logical Operators
- 3 Boolean NOT Operations: applies to one boolean operand
- 4 Demonstrates short-circuiting behavior
- 5 Demonstrate the boolean logical operators
- 6 Logical Operators
- 7 Logical operators in action
- 8 Logical OR Operations
- 9 The following table shows the effect of each logical operation
- 10 && versus &
AND operator
<source lang="java">
public class MainClass {
public static void main(String[] arg) {
int a = 0;
int b = 1;
if (a == 0 && b == 1) {
System.out.println("here");
} else {
System.out.println("there");
}
}
}</source>
here
Boolean Logical Operators
OperatorResult&Logical AND|Logical OR^Logical XOR (exclusive OR)||Short-circuit OR&&Short-circuit AND!Logical unary NOT&=AND assignment|=OR assignment^=XOR assignment==Equal to!=Not equal to?:Ternary if-then-else
Boolean NOT Operations: applies to one boolean operand
<source lang="java">
public class MainClass {
public static void main(String[] arg) {
int a = 0;
if (!(a == 0)) {
System.out.println("a is not 0");
} else {
System.out.println("a is 0");
}
}
}</source>
a is 0
Demonstrates short-circuiting behavior
<source lang="java">
public class MainClass {
static boolean test1(int val) {
System.out.println("test1(" + val + ")");
System.out.println("result: " + (val < 1));
return val < 1;
}
static boolean test2(int val) {
System.out.println("test2(" + val + ")");
System.out.println("result: " + (val < 2));
return val < 2;
}
static boolean test3(int val) {
System.out.println("test3(" + val + ")");
System.out.println("result: " + (val < 3));
return val < 3;
}
public static void main(String[] args) {
if (test1(0) && test2(2) && test3(2))
System.out.println("expression is true");
else
System.out.println("expression is false");
}
}</source>
test1(0) result: true test2(2) result: false expression is false
Demonstrate the boolean logical operators
<source lang="java">
public class MainClass {
public static void main(String args[]) {
boolean a = true;
boolean b = false;
boolean c = a | b;
boolean d = a & b;
boolean e = a ^ b;
boolean f = (!a & b) | (a & !b);
boolean g = !a;
System.out.println(" a = " + a);
System.out.println(" b = " + b);
System.out.println(" a|b = " + c);
System.out.println(" a&b = " + d);
System.out.println(" a^b = " + e);
System.out.println("!a&b|a&!b = " + f);
System.out.println(" !a = " + g);
}
}</source>
a = true b = false a|b = true a&b = false a^b = true !a&b|a&!b = true !a = false
Logical Operators
- You use logical operators to Combine a number of conditions.
- Logical operators operate on boolean values.
SymbolLong Name&logical AND&&conditional AND|logical OR||conditional OR!logical negation (NOT)
Logical operators in action
<source lang="java">
public class MainClass {
public static void main( String args[] )
{
// create truth table for && (conditional AND) operator
System.out.printf( "%s\n%s: %b\n%s: %b\n%s: %b\n%s: %b\n\n",
"Conditional AND (&&)", "false && false", ( false && false ),
"false && true", ( false && true ),
"true && false", ( true && false ),
"true && true", ( true && true ) );
// create truth table for || (conditional OR) operator
System.out.printf( "%s\n%s: %b\n%s: %b\n%s: %b\n%s: %b\n\n",
"Conditional OR (||)", "false || false", ( false || false ),
"false || true", ( false || true ),
"true || false", ( true || false ),
"true || true", ( true || true ) );
// create truth table for & (boolean logical AND) operator
System.out.printf( "%s\n%s: %b\n%s: %b\n%s: %b\n%s: %b\n\n",
"Boolean logical AND (&)", "false & false", ( false & false ),
"false & true", ( false & true ),
"true & false", ( true & false ),
"true & true", ( true & true ) );
// create truth table for | (boolean logical inclusive OR) operator
System.out.printf( "%s\n%s: %b\n%s: %b\n%s: %b\n%s: %b\n\n",
"Boolean logical inclusive OR (|)",
"false | false", ( false | false ),
"false | true", ( false | true ),
"true | false", ( true | false ),
"true | true", ( true | true ) );
// create truth table for ^ (boolean logical exclusive OR) operator
System.out.printf( "%s\n%s: %b\n%s: %b\n%s: %b\n%s: %b\n\n",
"Boolean logical exclusive OR (^)",
"false ^ false", ( false ^ false ),
"false ^ true", ( false ^ true ),
"true ^ false", ( true ^ false ),
"true ^ true", ( true ^ true ) );
// create truth table for ! (logical negation) operator
System.out.printf( "%s\n%s: %b\n%s: %b\n", "Logical NOT (!)",
"!false", ( !false ), "!true", ( !true ) );
}
}</source>
Conditional AND (&&) false && false: false false && true: false true && false: false true && true: true Conditional OR (||) false || false: false false || true: true true || false: true true || true: true Boolean logical AND (&) false & false: false false & true: false true & false: false true & true: true Boolean logical inclusive OR (|) false | false: false false | true: true true | false: true true | true: true Boolean logical exclusive OR (^) false ^ false: false false ^ true: true true ^ false: true true ^ true: false Logical NOT (!) !false: true !true: false
Logical OR Operations
The logical OR, ||, omits the evaluation of the right-hand operand when the left-hand operand is true.
<source lang="java">
public class MainClass {
public static void main(String[] arg) {
int value = 8;
int count = 10;
int limit = 11;
if (++value % 2 == 0 | ++count < limit) {
System.out.println("here");
System.out.println(value);
System.out.println(count);
}
System.out.println("there");
System.out.println(value);
System.out.println(count);
}
}</source>
there 9 11
The following table shows the effect of each logical operation
<source lang="java">
A B A | B A & B A ^ B !A
False False False False False True True False True False True False False True True False True True True True True True False False</source>
&& versus &
Conditional && will not evaluate the right-hand operand if the left-hand operand is false.
<source lang="java">
public class MainClass {
public static void main(String[] arg) {
int value = 8;
int count = 10;
int limit = 11;
if (++value % 2 == 0 & ++count < limit) {
System.out.println("here");
System.out.println(value);
System.out.println(count);
}
System.out.println("there");
System.out.println(value);
System.out.println(count);
}
}</source>
there 9 11
