# Replace Inefficient Constructors with valueOf()
# Description
All calls to a constructor of a primitive type will be replaced by the corresponding static valueOf() method. For example new Integer("1") becomes Integer.valueOf("1").
# Benefits
Using this rule saves memory and CPU cycles, as the constructors are not needed in this case. Furthermore, the constructors are deprecated in Java 9, which is an indication that they will eventually be removed from the language altogether.
# Tags
# Code Changes
# Number object types
The following change applies for Integer, Double, Float and Long.
Pre
new Integer(1);
new Integer("1");
Post
Integer.valueOf(1);
Integer.valueOf("1");
# Boolean objects
Pre
new Boolean(true);
new Boolean("true");
new Boolean(false);
new Boolean("false");
new Boolean("anyOtherStringThanTrue");
new Boolean((String) input);
new Boolean((Boolean) input);
Post
Boolean.valueOf(true);
Boolean.valueOf(true);
Boolean.valueOf(false);
Boolean.valueOf(false);
Boolean.valueOf(false);
Boolean.valueOf((String) input);
Boolean.valueOf((Boolean) input);
# Bytecode JDK 1.8
Pre
public void original() {
Integer val1 = new Integer(1);
Integer val2 = new Integer("1");
}
0 new #2 <java/lang/Integer>
3 dup
4 iconst_1
5 invokespecial #3 <java/lang/Integer.<init>>
8 astore_1
9 new #2 <java/lang/Integer>
12 dup
13 ldc #4 <1>
15 invokespecial #5 <java/lang/Integer.<init>>
18 astore_2
19 return
Post
public void transformed() {
Integer val1 = Integer.valueOf(1);
Integer val2 = Integer.valueOf("1");
}
0 iconst_1
1 invokestatic #6 <java/lang/Integer.valueOf>
4 astore_1
5 ldc #4 <1>
7 invokestatic #7 <java/lang/Integer.valueOf>
10 astore_2
11 return
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