Android Training Lesson Two notes

(Transferred from new blogger Education Huang Yuxin teacher)

1, ternary operator (trinocular operator):

Syntax: x?y:z; (it's just an expression);

Expression: cannot have an equal sign present, other types can be defined; it has only two types (values and types);

Note: int b=x?y:z; (At this point the y,z must be consistent with the type of B) there is no strict requirement for X, as long as it is a Boolean type;

2. If condition:

The execution process of code is divided into three kinds: sequential structure, selection structure and cyclic structure;

Syntax: (four types)

if (Boolean) {< statement block >};

if (Boolean) {< statement block >}else {< statement block >};

if (Boolean) {< statement block >}else if (Boolean) {< statement block >}....else if (Boolean) {};

if (Boolean) {}else if () {}...else{}

Note: 1, 3 kinds of do not necessarily output, and 2, 41 have one to be output; if conditions are "single-minded"

3, Switch: (case statement) (mainly JDK1.7)

Grammar:

Switch (can put any type 1) {

Case Type 1:

< statement block >

Break

Case Type 1:

< statement block >

Break

.....

Default

< statement block >

}

If there is no break this keyword, it can penetrate, continue to execute the following statement until a break or the end of the statement is encountered;

Note: efficiency: ternary operator >switch () >if ();

4. While loop:

Grammar:

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Note: When using while, you should pay attention to the control conditions of the loop, there is no statement after the dead loop;

5, do{< statement block >}while (expression);

Do.. while (): A statement is executed first, then judged; so anyway, it's going to be executed at least once;

While: the execution of the statement is judged before it is not necessarily executed;

Note: do..  while (); ";" This semicolon can not be less; suggestion: beginners do not use first;

6. For loop:

Grammar:

For (variable type variable name = initial value; number of cycles; step) {< statement block;}

Note: The step: is executed after the statement block is finished;

For,while cycle, can be used to each other;

When do I use for, and when to loop? (Personal advice)

A: For loop, the cyclic condition is more used, while loop, accumulate, judge the number of cycles;

7, Break,continue,return:

Break: Live in a switch or loop statement, indicating the end of the current loop;

Continue: Survive in the loop statement, indicating the end of the cycle, continue the next cycle;

Return: Live in a method with a return value, indicating the end of the entire method;

8. Static method:

Grammar:

Public +static +void/Type + method name (formal parameter/no parameter) {< statement block;}

Classification:

No return value: Must be modified with void;

Example:

public class a{

public static void F () {//cannot have return;}

public static void Main (string[] args) {

f ();//cannot assign value;

}

}

Has return value: Must have return type, return:

Example:

public class a{

public static int F () {

return int type;

}

public static void Main (string[] args) {

You can assign values:

int b=f ();//b=return returns the value;

}

}

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Android Training Lesson Two notes