Summary of the first three chapters of Java

The first chapter: 1. What's in Java?

The JDK (Java Development Kit) includes

Jre (Java Runtime Environment)---------->JVM (Java Virtual machine)

Application (JAVAC)

Java API and some common jar packages;

1. Java benefits: A. Object-oriented; cross-platform/portability for B.java;
2. Java execution Process: Java source file-------> Compiler-------->.class file--------->JVM explained.

Chapter II:

Variable:

Use a single letter or character to express words. The first thought of char;

String name = "Zhang San";

String name;

Name = "Zhang San";

int age = 18;

int age;

Age = 18;

char sex = ' male ';

char sex;

sex = ' woman '

mathematical operators +;-; *;/;%;+=; + +;--;

+ = is

sum = sum+ (num1+num2) is equivalent to sum+= (NUM1+NUM2)

Logical operator:>;  <;  >=;  <=;  !=; = = (two equals equals an equal sign is an assignment).

|| ;&&;

|| : Two conditions, meet one can be run;

&&: Two conditions are met to run.

identifiers :

1. Can contain numbers, letters, (_ and $ are not recommended for use);
2. Cannot begin with a number;
3. Cannot use Java keywords;
4. to have meaning;
5. Hump naming law;
6. Capitalize the first letter of the class name;

Chapter III:

1. Select structure: if structure; switch structure
2. A simple if statement:

If (condition) {

Statement

}；

If.......else statements

If (condition) {

}else{

}；

If.......else if........else Statements

If (condition) {

}else if (condition) {

}else{

}；

switch (expression) {

Case Value:

Break

Case Value:

Break

Case Value:

Break

Doufault:

break;

}

Loop structure:

While do........while for

For loop (fixed for loop count)

for (int i = 0; i< 10; i++) {

}

While is typically used in cases where the number of cycles is unknown;

Summary of the first three chapters of Java