Description

Checks that there is only one statement per line.

Rationale: It's very difficult to read multiple statements on one line.

In the Java programming language, statements are the fundamental unit of execution. All statements except blocks are terminated by a semicolon. Blocks are denoted by open and close curly braces.

OneStatementPerLineCheck checks the following types of statements: variable declaration statements, empty statements, import statements, assignment statements, expression statements, increment statements, object creation statements, 'for loop' statements, 'break' statements, 'continue' statements, 'return' statements, resources statements (optional).

Properties

Examples

To configure the check:

<module name="Checker">
  <module name="TreeWalker">
    <module name="OneStatementPerLine"/>
  </module>
</module>
        

The following examples will be flagged as a violation:

//Each line causes violation:
int var1; int var2;
var1 = 1; var2 = 2;
int var1 = 1; int var2 = 2;
var1++; var2++;
Object obj1 = new Object(); Object obj2 = new Object();
import java.io.EOFException; import java.io.BufferedReader;
;; //two empty statements on the same line.

//Multi-line statements:
int var1 = 1
; var2 = 2; //violation here
int o = 1, p = 2,
r = 5; int t; //violation here
        

An example of how to configure the check to treat resources in a try statement as statements to require them on their own line:

<module name="Checker">
  <module name="TreeWalker">
    <module name="OneStatementPerLine">
      <property name="treatTryResourcesAsStatement" value="true"/>
    </module>
  </module>
</module>
        

Note: resource declarations can contain variable definitions and variable references (from java9). When property "treatTryResourcesAsStatement" is enabled, this check is only applied to variable definitions. If there are one or more variable references and one variable definition on the same line in resources declaration, there is no violation. The following examples will illustrate difference:

OutputStream s1 = new PipedOutputStream();
OutputStream s2 = new PipedOutputStream();
// only one statement(variable definition) with two variable references
try (s1; s2; OutputStream s3 = new PipedOutputStream();) // OK
{}
// two statements with variable definitions
try (Reader r = new PipedReader(); s2; Reader s3 = new PipedReader() // violation
) {}
        

Example of Usage

• Google Style
• Checkstyle Style

Violation Messages

• multiple.statements.line

All messages can be customized if the default message doesn't suit you. Please see the documentation to learn how to.

Package

com.puppycrawl.tools.checkstyle.checks.coding

Parent Module

TreeWalker