How to use if and for loops?

1 Direct conversion

2 Forced conversion

byte -- short
                                                                                                                                     char
Left to right, direct conversion
Right to left, forced conversion
Boolean cannot be converted to other types

// Convert long to float directly (if the value of long is relatively large, convert it to float and use scientific notation to express it)

#                                          float f1 = l1; ## 　　 Float f2 = 3.14f;

　　 long l2 = (long)f2;

　　 System.out.println(l2);

--------------------------------------------- ------
Classification of statements in Java
1 Sequential statements
Statements from front to back Execute
2 branch statement
Select the appropriate statement to execute. if, if/else, if/else if/else, switch/case

3 Loop statement

Loop execution of a certain piece of code (including multiple statements). while, do/while, for

------------------------------ -----------------------
How to write if statement
1 Only if no else
if(score >= 60) {
System.out.println("pass");
}

2 An if and an else
if(score >= 60) {
System.out.println("pass");
 } else {
 System.out.println("Failed");
 }

3 if includes multiple else branches
if(score >= 90) {
System.out.println("Excellent");
 } else if(score >= 80) {
 System.out.println("Good");
 } else if(score >= 70) {
System.out.println("medium");
} else if(score >= 60) {
System.out.println("passed");
} else {
System.out.println("failed" ");
　}

Thinking: How to implement this code using switch...case...

------------------------------------------------ ---
switch case break default

Which data type is supported in switch
The standard is int, but also The following types can be supported
byte short int char String string
Note: boolean float double long

standard is not supported Syntax:
int value = 1;

## switch(value) {
case 1:
System.out.println("1");
break;
case 2:
System.out .println("2");
break;
default:
System.out.println("default");
　　　　　　　　break;
　　　　}

- - - - - - - - - - - - - - - - - - - - - - - - - - - -

Use the example of the above score To write switch case, it is

## 　　switch(score/10) {
　　　case 10:
　　　case 9:
System.out.println("Excellent");
break;
case 8:## System.out .println("moderate");
break;
case 6:
System.out.println("pass") ;
break;
case 5:
case 4:
case 3:
　　　　case 2:
　　　　case 1:
　　　　case 0:
　　　　System.out.println(" Failed");
　　　　　　　　　　
　　　 default:
　　　　 System.out.println("Exception score");
　　　　　　break;
　　　}

---------------- -------------------------------------
while
Initialization;

while(condition) {
Loop statement;
Iteration;

}

It should be noted that the conditional statement in while must be of boolean type
　　　 // Initialization
　　　int sum = 0;
　　　int i = 0;
　　　 // Start of loop
　　while(i < 100) {
System .out.println("sum="+sum);
do...while

Initialization
do {

Loop statement;

Iteration;

}while(condition);
　　　　　　　 // Initialization
　　　　　 int sum = 0;
　　　 int i = 0;
　　　　　　　 // Start of loop

　　　　　　　do {
　　　　　　　　　　　　
## 　　　　　　　　　
　　　sum = sum + 1;
　　　　　　　}while(i < 100);
for
for(initialization; condition; iteration) {
Loop statement
}

The various ways of writing for are as follows:

for The first way of writing
　　　　 // Initialization
　　int sum = 0;

　　for(int i = 0; i < = 100; i++) {
　　　　　　　　　　
　　　sum = sum + i;
　　}
System.out.println("sum="+sum);

The second way of writing for. The initialization condition is external
int sum = 0;
int i = 0;
　　for(; i <= 100; i++) {
　　　　 // Loop statement
　　 sum = sum + i;
　　}
　　System.out.println("sum="+sum);

## The third way of writing for. Built-in judgment statement
  // Initialization
 int sum = 0;
  for(int i = 0; ; i++) {
     if(i > 100) {
   break;
    }
    // Loop statement
　　　sum = sum + i;
　　}
　　System.out.println("sum="+sum);

The fourth way of writing for. Iteration statement built-in
　　　 // Initialization
　　int sum = 0;
　　for(int i = 0; i <= 100 ; ) {
　　　 　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　## 　　　　　　　
# 　　　i++;
　　}
　　System.out.println("sum="+sum);

The fifth way to write for. External initialization conditions, built-in judgment statements, and built-in iteration statements
　　　　　　　　　　　　　　　　　　　
　　int sum = 0;
　　int i = 0;
　　for(; ; ) {
　　　　 // Judgment statement
　　if(i > 100) {
break; ## 　　　　　　　　　　　　
　　i++;
　　}
　　System.out.println("sum="+ sum);

Thinking: Use a loop statement to print the following content
********
* ******

******

*****
****
***
**
*
hint:
System.out.println("*"); Prints a * sign without line breaks
System.out.print("*"); Prints a * sign without line breaks
System.out.println(); Line break
How many lines are printed? How many are printed per line?

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