[Java Getting Started Notes] Java Language Basics (3): Operators

Introduction

An operator is a special symbol. An operator is a specific symbol that operates one or more operands through certain operation rules and generates a result. The effective combination of an operator and operands is called an expression.

Operators in Java are mainly divided into the following categories:

Assignment operators

Arithmetic operators

Relational operators

Logical operators

Conditional operators (ternary operators)

Bitwise operators

Assignment operator

The assignment operator is used to assign a value to a variable or constant. The symbol of the assignment operator is "=".

Example

int a = 1;  //定义时直接赋值int b;int c;
b = 
c = 2;  //可以在一个语句内为多个变量赋值
int d = b + 3;   //变量运算后再赋值，先执行右边，再执行左边

Arithmetic operators

Java supports basic mathematical operations such as addition, subtraction, multiplication, division and remainder. They are the following:

Addition operator: +

double a = 1.1;double b = 1.2;double sum = a + b;
System.out.PRintln(sum); //Output 2.3

Subtraction operator: -

double a = 2.2;double b = 1.1;double sub = a - b;
System.out.println(sub); //Output 1.1

Multiplication operator: *

int a = 11;double b = 1.2;double multiply = a * b;
System.out.println(multiply); //Output 1.32

Division operator: /

The division operator is a bit special: if the operation Both values ​​​​are int, and the result obtained is also of type int. The decimal point will be removed directly and will not be rounded.

int a = 10; int b = 4; double c = a/b; System.out.println(c); //The original result of 10chu 4 is 2.5, but the result of dividing two int type numbers is an int type number. Although the result value is assigned to double,
　　　　　　　　　　//But the output result becomes 2.0, which is equivalent to removing the decimal point when the operation is completed, and then converting it to 2.0double a2 = 5.2;double b2 = 3.1;double c2 = a2/b2; System.out.println(c2); //Operation on two double values, output result: 1.6774193548387097System.out.println(5 / 0.0); //The divisor is double type 0.0, and the output is negative infinity System.out.println(5 / 0); //If the divisor is 0, an error will be reported during runtime

Remainder operator: %

int a = 5;int b = 3;double c = 3.2;
System.out.println(a%b) ; //Output 2System.out.println(a%c); //1.7999999999999998System.out.println(0%5); //Output 0System.out.println(5%0); //An error will occur during operation

Find the negative: -

int i = -1;int i2 = -i;
System.out.println(i2); //Output 1

Self-increment: ++

int i = 1;
i++ ; //Equivalent to adding 1 to the value of i; System.out.println(i); //Output 2

The self-increasing symbol can be placed in front of the variable or behind the variable. Put it in front first Add 1 to the operand, and then perform the operation of the expression. Putting it after it will do the opposite.

int i1 = 1;int i2 = 1;int i3 = i1++; //At this time, the value of i3 is 1 and the value of i1 is 2; it first assigns the value of i1 to i3, and then adds 1 to i1 ;int i4 = ++i2; //At this time, the value of i4 is 2, and the value of i2 is also 2; it first adds 1 to the value of i2, and then assigns the value to i4;

Decrement: --

The function is similar to self-adding

int i1 = 1;int i2 = 1;int i3 = i1++; //At this time, the value of i3 is 1 and the value of i1 is 0; it first assigns the value of i1 to i3, then decrement i1 by 1; int i4 = ++i2; //At this time, the value of i4 is 0, and the value of i2 is also 0; it first decrements the value of i2 by 1, and then assigns the value to i4;

Relational operators (comparison operators)

Relational operators can test the relationship between two operands (but will not change the value of the operand). The result of the relational expression is boolean true/false:

System.out.println(4 == 4); //The result is trueSystem.out.println(4 != 3); //The result is trueSystem.out.println(true == false); //The result is false

Logical operators

Logical operators are used to operate boolean type variables or constants

See examples

System.out.println(!true); //The result is falseSystem.out.println (2 > 1 && 1 > 1); //The result is falseSystem.out.println(2 > 1 || 1 > 1); //The result is trueSystem.out.println(true ^ false); / /The result is true, XOR, which is equivalent to inverting the first previous value true, and then performing an "OR" operation

Let's take a look at the difference between | and ||

int a = 1; int b = 1;if(a == 1 | b++ > 1){
System.out.println(b); //The output value of b is 2, bitwise OR, although the result on the left side of the | symbol is true, it still Will execute the code to the right of the | symbol}

and change | to ||

int a = 1;int b = 1;if(a == 1 || b++ > 1){
System.out.println(b); //The output value of b is 1, and the result on the left side of the || symbol is true, the code to the right of the || symbol will no longer be executed}

Conditional operator (ternary operator)

Its general form is:

Expression 1 ? Expression 2 : Expression 3

Determine whether to execute expression 2 or expression 3 based on the result of expression 1. If the result of expression 1 is true, execute expression 2, otherwise execute expression 3;

Conditional operators can be substituted in some cases Small if...else statement.

String s = 1 > 2 ? "1 is greater than 2" : "1 is not greater than 2";
System.out.println(s); //Output 1 is not greater than 2

bit operator

bit operation Symbols are two data that participate in operations, and operations are performed based on binary bits. There are seven bitwise operators in Java: bitwise AND (&), bitwise OR (|), bitwise NOT (~), bitwise XOR (^), left shift operator (>), unsigned right shift operator (>>>).

For detailed introduction, please refer to the following article:

http://www.cnblogs.com/yezhenhan/archive/2012/06/20/2555849.html

Priority of operators

In many cases , an expression consists of multiple operators, and the priority determines the calculation order of the operators:

Although operators have priorities, an expression will be evaluated sequentially according to the priority of the expression operators, but In actual programming, if an expression is very long, it is not recommended to write it like this. Instead, it is written in several steps, because the readability is too poor when written together.

The above is [Java Introduction Notes] Java Language Basics (3): The content of operators. For more related content, please pay attention to the PHP Chinese website (www.php.cn)!