Reference kinds

The total number of Java references kinds is 34×2=68. Table 2 lists the OpenUnderstand Java reference kinds, the kind names, and the kind examples for use with the Python API.

Table 2. Java references kinds details

Reference kind full name	Description	Example code snippet
Java Call/Callby	Indicates an invocation of a method.	Call and Callby
Java Call/Callby Nondynamic	Indicates a non-dynamic invocation of a method.	Java Call Nondynamic and Callby Nondynamic
Java Cast/Castby	Indicates a type is used to cast an instance to a different type.	Java Cast and Castby
Java Contain/Containin	Indicates a class is in a package.	Java Contain and Containin
Java Couple/Coupleby	Indicates a coupling link as counted in the OO coupling metrics. A link is created from a class to any external class (a class that is not in the extends/implements hierarchy) that is referenced.	Java Couple and Coupleby
Java Extend Couple/Coupleby Java Extend Couple/Coupleby External Java Extend Couple/Coupleby Implicit Java Extend Couple/Coupleby Implicit External	Indicates one class or interface extends another. This extends relation is used when the extended class is in a file that is part of the project. If the extended class was found in a classpath .jar file, the relation is Java Extend Couple External. If the Indicates class implicitly extends the java.lang.Object class, the relation is Java Extend Couple Implicit.	Java Extend Couple and Extendby Coupleby
Java Implement Couple/Coupleby	Indicates a class implements an interface.	Java Implement Couple and Implementby Coupleby
Java Create/Createby	Indicates that an instance of a class is created (“new” operator) in a scope.	Java Create and Createby
Java Declare/Declarein	Indicates that a package is declared in a file or in a (parent) package.	Java Declare and Declarein
Java Define/Definein	Indicates that an entity is defined in a scope.	Java Define and Definein
Java Define/Definein Implicit	Todo:	Java Define and Definein Implicit
Java DotRef/DotRefby	Indicates that an entity name was used to the left of a “.” in a qualified name.	Java DotRef and DotRefby
Java Export/Exportby	Todo:	Java Export and Exportby
Java Import/Importby Java Import/Importby Demand	Java Import indicates a file imports an individual class. For example, the some_file.java file might contain: import pack1.some_class; Java Import Demand indicates a file has an on-demand import statement for a package or class. For example, the some_file.java file might contain: import pack1.*;	Java Import and Importby
Java Modify/Modifyby	Indicates that a variable’s value is modified or both read and set, as with the increment (++), decrement (--), and assignment/operator combinations (*=, /=, ...).	Java Modify and Modifyby
Java ModuleUse/ModuleUseby	Todo:	Java ModuleUse and ModuleUseby
Java Override/Overrideby	Indicates that a method overrides a method from a parent class.	Java Override and Overrideby
Java Provide/Provideby	Todo:	Java Provide and Provideby
Java Require/Requireby	Todo:	Java Require and Requireby
Java Set/Setby	Java Set indicates that a variable is set by a separate statement.	Java Set and Setby
Java Set/Setby Init	Java Set Init indicates that a variable is initialized in its declaration.	Java Set Init and Setby Init
Java Set/Setby Partial	Todo:	Java Set Partial and Setby Partial
Java Typed/Typedby	Indicates the type of a variable or parameter.	Java Typed and Typedby
Java Use/Useby	Indicates that a variable is used or read.	Java Use and Useby
Java Use/Useby Partial	Todo:	Java Use Partial and Useby Partial
Java Use/Useby Ptr	Todo:	Java Use Ptr and Useby Ptr
Java Use/Useby Return	Todo:	Java Use Return and Useby Return
Java Open/Openby	Todo:	Java Open and Openby
Java Throw/Throwby	Indicates that a method throws an exception.	Java Throw and Throwby
Java End	Indicates the end of a class, interface, or method.	Java End and Endby

Reference kind examples

This section describes the example in Table 2 with more details.

Call and Callby

Indicates an invocation of a method.

class class1 {
 void meth1() {
  ...
 }
}
class class2 {
 class1 some_obj;
 void meth2() {
  some_obj.meth1();
 }
}

Reference kind string	Entity performing references	Entity being referenced
Java Call	meth2	meth1
Java Callby	meth1	meth2

Java Call Nondynamic and Callby Nondynamic

Indicates a non-dynamic invocation of a method.

class class1 {
 void meth1() {
  ...
 }
}
class class2 extends class1 {
 class1 some_obj;
 void meth1() {
  super.meth1();
 }
}

Reference kind string	Entity performing references	Entity being referenced
Java Call Nondynamic	class2.meth1	class1.meth1
Java Callby Nondynamic	class1.meth1	class2.meth1

Java Cast and Castby

Indicates a type is used to cast an instance to a different type.

class c1 {
 ...
}
class c2 extends c1 {
 ...
}
class c3 {
 c2 b = new c2();
 c1 a = (c1) b;
}

Reference kind string	Entity performing references	Entity being referenced
Java Cast	c3	c1
Java Castby	c1	c3

Java Contain and Containin

Indicates a class is in a package.

package some_pack;

class some_class {
 ...
}

Reference kind string	Entity performing references	Entity being referenced
Java Contain	some_pack	some_class
Java Containin	some_class	some_pack

Java Couple and Coupleby

Indicates a coupling link as counted in the OO coupling metrics. A link is created from a class to any external class (a class that is not in the extends/implements hierarchy) that is referenced.

public class c1 {
 ...
}

public class c2 {
 cl obj;
}

Reference kind string	Entity performing references	Entity being referenced
Java Couple	c2	c1
Java Coupleby	c1	c2

Java Extend Couple and Extendby Coupleby

Indicates one class or interface extends another. This extends relation is used when the extended class is in a file that is part of the project. If the extended class was found in a classpath .jar file, the relation is Java Extend Couple External. If the Indicates class implicitly extends the java.lang.Object class, the relation is Java Extend Couple Implicit.

• [ ] Todo: add a short definition with and an example code and corresponding table for Java Extend Couple Implicit External and Java Extendby Coupleby Implicit External reference kind.

// Example 1:
class class1 {
 ...
}
class class2 extends class1 {
 ...
}
// Example 2:
class some_class extends java.io.Writer {
 ...
}
// Example 3:
class some_class {
 ...
}
// Example 4:
//Todo

Reference kind string	Entity performing references	Entity being referenced
Java Extend Couple	Ex 1: class2	Ex 1: class2
Java Extendby Coupleby	Ex 1: class1	Ex 1: class1
Java Extend Couple External	Ex 2: some_class	Ex 2: java.io.Writer
Java Extendby Coupleby External	Ex 2: java.io.Writer	Ex 2: some_class
Java Extend Couple Implicit	Ex 3: some_class	Ex 3: java.lang.Object
Java Extendby Coupleby Implicit	Ex 3: java.lang.Object	Ex 3: some_class
Java Extend Couple Implicit External	Todo	Todo
Java Extendby Coupleby Implicit External	Todo	Todo

Java Implement Couple and Implementby Coupleby

Indicates a class implements an interface.

interface some_interface {
 ...
}

class some_class implements some_interface {
 ...
}

Reference kind string	Entity performing references	Entity being referenced
Java Implement Couple	some_class	some_interface
Java Implementby Coupleby	some_interface	some_class

Java Create and Createby

Indicates that an instance of a class is created (new operator) in a scope.

class c1 {
 ...
}

class c2 {
 c1 a = new c1();
}

Reference kind string	Entity performing references	Entity being referenced
Java Create	c2	c1
Java Createby	c1	c2

Java Declare and Declarein

Indicates that a package is declared in a file or in a (parent) package.

package technology.tabula.debug;

import java.awt.BasicStroke;
import java.awt.Color;

class Debug {
...
}

Reference kind string	Entity performing references	Entity being referenced
Java Declare	Debug.java	technology, technology.tabula.debug
Java Declarein	technology, technology.tabula.debug	Debug.java

Java Define and Definein

Indicates that an entity is defined in a scope.

//Example Define
class some_class {
 int some_var = 5;
}

//Example Define implicit
//Todo

• [ ] Todo: add a short definition with and an example code and corresponding table for Define Implicit and Definein Implicit reference kind.

Reference kind string	Entity performing references	Entity being referenced
Java Define	some_class	some_var
Java Definein	some_var	some_class
Java Define Implicit	Todo:	Todo:
Java Definein Implicit	Todo:	Todo:

Java DotRef and DotRefby

Indicates that an entity name was used to the left of a “.” in a qualified name.

package some_pack;
class class1 {
 static int covid;
}

class class2 {
 void some_meth() {
  some_pack.class1.covid = 2021;
 }
}

Reference kind string	Entity performing references	Entity being referenced
Java DotRef	some_meth	some_pack
Java DotRefby	some_pack	some_meth

Java Export and Exportby

• [ ] Todo: add a short definition with and an example code and corresponding table for this reference kind.

Java Import and Importby

Java Import indicates a file imports an individual class. For example, the some_file.java file might contain:

import pack1.some_class;

Java Import Demand indicates a file has an on-demand import statement for a package or class. For example, the some_file.java file might contain:

import pack1.*;

Reference kind string	Entity performing references	Entity being referenced
Java Import	some_file	pack1.some_class
Java Importby	pack1.some_class	some_file
Java Import Demand	some_file	pack1
Java Importby Demand	pack1	some_file

Java Modify and Modifyby

Indicates that a variable’s value is modified or both read and set, as with the increment (++), decrement (--), and assignment/operator combinations (*=, /=, ...).

class some_class {
 void some_meth() {
  int i = 5;
  i++;
 }
}

Reference kind string	Entity performing references	Entity being referenced
Java Modify	some_meth	i
Java Modifyby	i	some_meth

Modify (Deref) Partial and Modifyby (Deref) Partial

This reference is like Modify and Modifyby. But, it is used when an entity modifies some elements of a variable of collection type.

public ProjectionProfile{
  this.verticalProjection = new float[toFixed(areaHeight)];
  this.horizontalProjection = new float[toFixed(areaWidth)];

 private void addRectangle(Rectangle element) {
        // calculate horizontal and vertical projection profiles
        if (!area.contains(element)) {
            return;
        }

        this.minCharHeight = (float) Math.min(this.minCharHeight, element.getHeight());
        this.minCharWidth = (float) Math.min(this.minCharWidth, element.getWidth());

        for (int k = toFixed(element.getLeft()); k < toFixed(element.getRight()); k++) {
            this.horizontalProjection[k - toFixed(areaLeft)] += element.getHeight();
            this.maxHorizontalProjection = Math.max(this.maxHorizontalProjection, this.horizontalProjection[k - toFixed(areaLeft)]);
        }
    }     
}

Reference kind string	Entity performing references	Entity being referenced
Java Modify Partial	addRectangle	horizontalProjection
Java Modifyby Partial	horizontalProjection	addRectangle

Java ModuleUse and ModuleUseby

• [ ] Todo: add a short definition with and an example code and corresponding table for this reference kind.

Java Override and Overrideby

Indicates that a method overrides a method from a parent class.

class A {
 int some_meth() {
 ...
 }
}

class B extends A{
 int some_meth() {
 ...
 }
}

Reference kind string	Entity performing references	Entity being referenced
Java Override	B.some_meth	A.some_meth
Java Overrideby	A.some_meth	B.some_meth

Java Provide and Provideby

• [ ] Todo: add a short definition with and an example code and corresponding table for this reference kind.

Java Require and Requireby

• [ ] Todo: add a short definition with and an example code and corresponding table for this reference kind.

Java Set and Setby

Java Set indicates that a variable is set by a separate statement.

void some_meth() {
 int i;
 i = 5;
}

Java Set Init indicates that a variable is initialized in its declaration.

void some_meth() {
 int i = 5;
}

• [ ] Todo: add a short definition with and an example code and corresponding table for Set Partial and Setby Partial reference kinds.

Reference kind string	Entity performing references	Entity being referenced
Java Set	some_meth	i
Java Setby	i	some_meth
Java Set Init	some_meth	i
Java Setby Init	i	some_meth
Set Partial	Todo:	Todo:
Setby Partial	Todo:	Todo:

Java Typed and Typedby

Indicates the type of a variable or parameter.

class class1 {
 ...
}

class class2 {
 class1 some_obj;
}

Reference kind string	Entity performing references	Entity being referenced
Java Typed	some_obj	class1
Java Typedby	class1	some_obj

Java Use and Useby

Indicates that a variable is used or read.

class some_class {
 int some_var;
 void some_meth() {
  int local_var = some_var; // read of some_var
 }
}

• [ ] Todo: add a short definition with and an example code and corresponding table for Use Partial and Useby Partial reference kinds.
• [ ] Todo: add a short definition with and an example code and corresponding table for Use Ptr and Useby Ptr reference kinds.
• [ ] Todo: add a short definition with and an example code and corresponding table for Use Return and Useby Return reference kinds.

Reference kind string	Entity performing references	Entity being referenced
Java Use	some_meth	some_var
Java Useby	some_var	some_meth
Java Use Partial	Todo:	Todo:
Java Useby Partial	Todo:	Todo:
Java Use Ptr	Todo:	Todo:
Java Useby Partial	Todo:	Todo:
Java Use Return	Todo:	Todo:
Java Useby Return	Todo:	Todo:

Java Open and Openby

• [ ] Todo: add a short definition with and an example code and corresponding table for this reference kind.

Java Throw and Throwby

Indicates that a method throws an exception.

void some_meth() throws java.io.IOException {
 ...
}

Reference kind string	Entity performing references	Entity being referenced
Java Throw	some_meth	java_io.IOException
Java Throwby	java_io.IOException	some_meth

Java End and Endby

Indicates the end of a class, interface, or method.

• [ ] Todo: Requires a better example (I cannot understand this kind in understand!)

Reference kind string	Entity performing references	Entity being referenced
Java End	some_class	some_class
Java Endby	some_class	some_class

References

[1] SciTools, “Understand,” 2020. https://www.scitools.com/ (accessed Sep. 11, 2020).