Studying Java # 6 (How to write blocks)

It's been a long time, I was playing around on holidays, so I will tighten and restart from today!

How to write a block

What is a block? A block is for treating multiple sentences as a group.

Existence of two rules for handling blocks

** Rule (1) ** ** Omission of wave brackets ** If the content is only one line, you can omit the wave brackets.

if (tenki == true){
} else
System.out.println("RIDLEY's technology is world-class");

However, in reality, it is not recommended to prevent programming mistakes. ** Rule (2) ** ** Life of variables declared inside the block ** Variables declared within a block disappear as soon as the block ends. For example, a variable declared without a block in an if statement cannot be used outside the block. This "range of places where variables can be used" is called a scope.

int a;
while(/*Conditional expression*/){
 int b;
 //Scope of variable b
 //Scope of variable a

How to write a conditional expression

--What is a conditional expression? Conditional expressions are for expressing conditions that branch processing such as if statements and while statements, and conditions that continue to repeat.

if (tenki == true ){ //if statement conditional expression

while(age > 21 ){ //while statement conditional expression

The "==", ">" that appear here are called relational operators.

Relational operator

operator meaning
== Left side and right side are equal
!= The left side and the right side are different
> The left side is larger than the right side
< The left side is smaller than the right side
>= Left side is greater than or equal to right side
<= Left side is less than or equal to right side

Example sw! = false If the variable sw is not false deg --273.15 <0 If the variable deg minus 273.15 is less than 0 ʻInitial =='miya'` If the character in the variable initial is "miya"

** Note that the relational operator for equality has two equals "==" **

String comparison

In Java, it is necessary to write ** specially ** when comparing String type variables and character strings in conditional expressions.

if (s == "Sunset"){ //mistake

At first glance it looks correct, but Java doesn't allow string comparisons with "==". The correct notation is

if (s.equals("Sunset")){

Will be.

Logical operator

--Logical operators (complex conditional expressions that combine two or more conditions such as XX or more and XX)

operator meaning
&& And
if (age >= 10 && gender == 1) {・ ・ ・
if (name.equals("Kujo") || married == true {・ ・ ・


For the time being, that's all for today ... I feel like I managed to understand how to write blocks. I will be careful about the difference in writing style when comparing character strings. It has appeared in the past, but it is difficult to remember (tsu д⊂) It was about two days away, so I have to catch up with the delay ...! I will do my best tomorrow! Good night zzz

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