Control Flow Statements - Java Tutorial 5.0 英文版

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Control Flow Statements

When writing a program, you type statements into a file. Without control flow statements, the interpreter executes the statements in the order they appear in the file from left to right, top to bottom. You can use control flow statements in your programs to conditionally execute statements; to repeatedly execute a block of statements; and to otherwise change the normal, sequential flow of control. For example, in the following code snippet, the if statement conditionally executes the System.out.println statement within the braces based on the return value of Character.isUpperCase(aChar).

char aChar;
...
if (Character.isUpperCase(aChar)) {
    System.out.println("The character " + aChar
                       + " is uppercase.");
}

The Java programming language provides several control flow statements, which are listed in the following table.

Control Flow Statements

Statement Type	Keyword
looping	while, do-while, for
decision making	if-else, switch-case
exception handling	try-catch-finally, throw
branching	break, continue, label:, return

In the sections that follow, the notation here is used to describe the general form of a control flow statement.

control flow statement details {
    statement(s)
}

Technically, braces — { and } — are not required if the block contains only one statement. However, we recommend that you always use the braces because the code is easier to read and they help prevent errors when modifying code.

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