Java operators

One of the most basic uses of computers is to perform mathematical operations. As a computer language, Java also provides a rich set of operators to manipulate variables. We can divide operators into the following groups:

• arithmetic operators
• Relational operators
• Bit operators
• Logical operators
• assignment operator
• Other operators

arithmetic operators

Arithmetic operators are used in mathematical expressions and they work the same way they do in mathematics. The following table lists all arithmetic operators.

The example in the table assumes that the integer variable A has a value of 10 and the variable B has a value of 20:

Although both are self-increasing (their operation results are equal to B+1), there are still differences between B++ and ++B. ++B is an lvalue and operates directly in place (can be understood as + directly on variable B 1), B++ is an rvalue. When operating in the compiler, a temporary variable will be constructed first, and then the temporary variable will be used to calculate +1 and then assigned to B.

Therefore, in the example code below, when printing d++, it is found that the result is not +1 (the variable d is printed at this time, and the temporary variable of d is operated), but the result displayed in the next printed statement is +1 again. The final result (the value of the temporary variable is assigned to variable d). The result of printing ++d is directly +1.

Example

The following simple example program demonstrates arithmetic operators. Copy and paste the following Java program and save it as a Test.java file, then compile and run the program:

 public class Test { public static void main(String args[]) { int a = 10; int b = 20; int c = 25; int d = 25; System.out.println("a + b = " + (a + b) ); System.out.println("a - b = " + (a - b) ); System.out.println("a * b = " + (a * b) ); System.out.println("b / a = " + (b / a) ); System.out.println("b % a = " + (b % a) ); System.out.println("c % a = " + (c % a) ); System.out.println("a++ = " + (a++) ); System.out.println("a-- = " + (a--) ); // 查看d++ 与++d 的不同System.out.println("d++ = " + (d++) ); System.out.println("d = " + d); System.out.println("++d = " + (++d) ); } }

The compilation and running results of the above example are as follows:

 a + b = 30 a - b = -10 a * b = 200 b / a = 2 b % a = 0 c % a = 5 a++ = 10 a-- = 11 d++ = 25 d =26 ++d = 27

Relational operators

The following table shows the relational operators supported by Java

The example integer variable A in the table has a value of 10 and variable B has a value of 20:

Example

The following simple example program demonstrates relational operators. Copy and paste the following Java program and save it as a Test.java file, then compile and run the program:

 public class Test { public static void main(String args[]) { int a = 10; int b = 20; System.out.println("a == b = " + (a == b) ); System.out.println("a != b = " + (a != b) ); System.out.println("a > b = " + (a > b) ); System.out.println("a < b = " + (a < b) ); System.out.println("b >= a = " + (b >= a) ); System.out.println("b <= a = " + (b <= a) ); } }

The compilation and running results of the above example are as follows:

 a == b = false a != b = true a > b = false a < b = true b >= a = true b <= a = false

Bit operators

Java defines bitwise operators, which apply to integer types (int), long integers (long), short integers (short), character types (char), and byte types (byte).

Bitwise operators operate on all bits and operate bitwise. Assume a = 60, and b = 13; their binary format representation will be as follows:

 A = 0011 1100 B = 0000 1101 ----------------- A&B = 0000 1100 A | B = 0011 1101 A ^ B = 0011 0001 ~A= 1100 0011

The following table lists the basic operations of bitwise operators, assuming that the integer variable A has a value of 60 and the variable B has a value of 13:

Example

The following simple example program demonstrates bitwise operators. Copy and paste the following Java program and save it as a Test.java file, then compile and run the program:

 public class Test { public static void main(String args[]) { int a = 60; /* 60 = 0011 1100 */ int b = 13; /* 13 = 0000 1101 */ int c = 0; c = a & b; /* 12 = 0000 1100 */ System.out.println("a & b = " + c ); c = a | b; /* 61 = 0011 1101 */ System.out.println("a | b = " + c ); c = a ^ b; /* 49 = 0011 0001 */ System.out.println("a ^ b = " + c ); c = ~a; /*-61 = 1100 0011 */ System.out.println("~a = " + c ); c = a << 2; /* 240 = 1111 0000 */ System.out.println("a << 2 = " + c ); c = a >> 2; /* 215 = 1111 */ System.out.println("a >> 2 = " + c ); c = a >>> 2; /* 215 = 0000 1111 */ System.out.println("a >>> 2 = " + c ); } }

The compilation and running results of the above example are as follows:

 a & b = 12 a | b = 61 a ^ b = 49 ~a = -61 a << 2 = 240 a >> 2 = 15 a >>> 2 = 15

Logical operators

The following table lists the basic operations of logical operators, assuming that Boolean variable A is true and variable B is false

Example

The following simple example program demonstrates logical operators. Copy and paste the following Java program and save it as a Test.java file, then compile and run the program:

 public class Test { public static void main(String args[]) { boolean a = true; boolean b = false; System.out.println("a && b = " + (a&&b)); System.out.println("a || b = " + (a||b) ); System.out.println("!(a && b) = " + !(a && b)); } }

The compilation and running results of the above example are as follows:

 a && b = false a || b = true !(a && b) = true

assignment operator

The following are the assignment operators supported by the Java language:

Example

The following simple example program demonstrates the assignment operator. Copy and paste the following Java program and save it as a Test.java file, then compile and run the program:

 public class Test { public static void main(String args[]) { int a = 10; int b = 20; int c = 0; c = a + b; System.out.println("c = a + b = " + c ); c += a ; System.out.println("c += a = " + c ); c -= a ; System.out.println("c -= a = " + c ); c *= a ; System.out.println("c *= a = " + c ); a = 10; c = 15; c /= a ; System.out.println("c /= a = " + c ); a = 10; c = 15; c %= a ; System.out.println("c %= a = " + c ); c <<= 2 ; System.out.println("c <<= 2 = " + c ); c >>= 2 ; System.out.println("c >>= 2 = " + c ); c >>= 2 ; System.out.println("c >>= a = " + c ); c &= a ; System.out.println("c &= a= " + c ); c ^= a ; System.out.println("c ^= a= " + c ); c |= a ; System.out.println("c |= a= " + c ); } }

The compilation and running results of the above example are as follows:

 c = a + b = 30 c += a = 40 c -= a = 30 c *= a = 300 c /= a = 1 c %= a = 5 c <<= 2 = 20 c >>= 2 = 5 c >>= 2 = 1 c &= a = 0 c ^= a = 10 c |= a = 10

Conditional operator (?:)

Conditional operators are also known as ternary operators. This operator has three operands and needs to evaluate the value of a Boolean expression. The main purpose of this operator is to decide which value should be assigned to the variable.

 variable x = (expression) ? value if true : value if false

Example

 public class Test { public static void main(String args[]){ int a , b; a = 10; b = (a == 1) ? 20: 30; System.out.println( "Value of b is : " + b ); b = (a == 10) ? 20: 30; System.out.println( "Value of b is : " + b ); } }

The compilation and running results of the above example are as follows:

 Value of b is : 30 Value of b is : 20

instanceof operator

This operator is used to operate on object instances and check whether the object is of a specific type (class type or interface type).

The instanceof operator is used in the following format:

 ( Object reference variable ) instanceof (class/interface type)

If the object pointed to by the variable on the left side of the operator is an object of the class or interface (class/interface) on the right side of the operator, the result is true.

Here's an example:

 String name = 'James'; boolean result = name instanceof String; // 由于name是String类型，所以返回真

This operator still returns true if the compared objects are compatible with the right-hand type.

Look at the following example:

 class Vehicle {} public class Car extends Vehicle { public static void main(String args[]){ Vehicle a = new Car(); boolean result = a instanceof Car; System.out.println( result); } }

The compilation and running results of the above example are as follows:

 true

Java operator precedence

When multiple operators appear in an expression, which one comes first? This involves the issue of operator precedence. In a multi-operator expression, different operator priorities will lead to very different final results.

For example, (1+3) + (3+2)*2, if this expression is calculated according to the plus sign as the highest priority, the answer is 18, and if the multiplication sign is the highest priority, the answer is 14.

Another example, x = 7 + 3 * 2; here x gets 13, not 20, because the multiplication operator has a higher priority than the addition operator, so 3 * 2 is calculated first to get 6, and then 7 is added.

The operators with the highest precedence in the following table are at the top of the table, and the operators with the lowest precedence are at the bottom of the table.