Java Tutorial/Statement Control/If Statement
Содержание
Expression indentation for if statement
If the expression is too long, you can use two units of indentation for subsequent lines.
<source lang="java">
public class MainClass {
public static void main(String[] args) {
int numberOfLoginAttempts = 10;
int numberOfMinimumLoginAttempts = 12;
int numberOfMaximumLoginAttempts = 13;
int y = 3;
if (numberOfLoginAttempts < numberOfMaximumLoginAttempts
|| numberOfMinimumLoginAttempts > y) {
y++;
}
}
}</source>
Multiple selections
If there are multiple selections, you can also use if with a series of else statements.
<source lang="java">
if (booleanExpression1) {
// statements
} else if (booleanExpression2) {
// statements
} ... else {
// statements
}</source>
Nested if Statements
<source lang="java">
public class MainClass {
public static void main(String[] arg) {
int a = 2;
if (a == 0) {
System.out.println("in the block");
if (a == 2) {
System.out.println("a is 0");
} else {
System.out.println("a is not 2");
}
} else {
System.out.println("a is not 0");
}
}
}</source>
a is not 0
The else Clause
<source lang="java">
public class MainClass {
public static void main(String[] arg) {
int a = 0;
if (a == 0) {
System.out.println("in the block");
System.out.println("in the block");
} else {
System.out.println("a is not 0");
}
}
}</source>
in the block in the block
The if Statement in action
<source lang="java">
public class MainClass {
public static void main(String[] arg) {
int a = 0;
if (a == 0) {
System.out.println("a is 0");
}
}
}</source>
a is 0
The if statement syntax
The if statement is a conditional branch statement. The syntax of the if statement is either one of these two:
<source lang="java">
if (booleanExpression) {
statement (s)
}</source>
Using braces makes your "if" statement clearer
If there is only one statement in an if or else block, the braces are optional.
<source lang="java">
public class MainClass {
public static void main(String[] args) {
int a = 3;
if (a > 3)
a++;
else
a = 3;
}
}</source>
Using && in if statement
<source lang="java">
public class MainClass {
public static void main(String[] arg) {
int value = 8;
int count = 10;
int limit = 11;
if (++value % 2 == 0 && ++count < limit) {
System.out.println("here");
System.out.println(value);
System.out.println(count);
}
System.out.println("there");
System.out.println(value);
System.out.println(count);
}
}</source>
there 9 10
Using || (or operator) in if statement
<source lang="java">
public class MainClass {
public static void main(String[] arg) {
int value = 8;
int count = 10;
int limit = 11;
if (++value % 2 != 0 || ++count < limit) {
System.out.println("here");
System.out.println(value);
System.out.println(count);
}
System.out.println("there");
System.out.println(value);
System.out.println(count);
}
}</source>
here 9 10 there 9 10
