# Replace Equality Check with isEmpty()

# Description

This rule replaces comparisons of length() or size() with 0 with a call to isEmpty(). Any occurrences of such a comparison will be replaced, regardless of surrounding control structure.

# Benefits

The time complexity of any isEmpty() method implementation should be O(1) whereas some implementations of size() can be O(n). Thus, using this rule provides performance benefits.

# Tags

# Code Changes

# size, length


Map<String, String> m = new HashMap<>();
if(m.size() == 0);
String s = "";
if(s.length() == 0);


Map<String, String> m = new HashMap<>();
String s = "";

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You can apply this refactoring for free with the jSparrow Eclipse IDE plug-in.
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# Properties

Property Value
Rule ID UseIsEmptyOnCollections
First seen in jSparrow version 2.0.2
Minimum Java version 6
Remediation cost 2 min