Below are BooleanCompareNode.java, VariableReferenceNode.java, IfNode.java, RepeatNode.java, & WhileNode.java. Attached is an image where it's circled in blue all the methods that must be implemented in the java files that are presented below:     BooleanCompareNode.java public class BooleanCompareNode extends Node { enum CompareType { eq, ne, lt, gt, le, ge }; CompareType type; Node left; Node right; public BooleanCompareNode(CompareType type, Node left, Node right) { this.type = type; this.left = left; this.right = right; } public String ToString() { return left.toString() + type.toString() + right.toString(); }   }     VariableReferenceNode.java public class VariableReferenceNode extends Node{ String name; Node arrayIndex; public VariableReferenceNode(String name) { this.name = name; this.arrayIndex = arrayIndex; } public String ToString() { String indexString = (arrayIndex == null) ? "" : "[" + arrayIndex.toString() + "]"; return name + indexString; } public void setIndex(Node indexExpr) { } public String getVariableName() { return null; } }   IfNode.java   import java.util.ArrayList; import java.util.List;   public class IfNode extends Node{ private BooleanCompare condition; private ArrayList statements; private IfNode nextIf; public IfNode(BooleanCompare condition, ArrayList statements, IfNode nextIf) { this.condition = condition; this.statements = statements; this.nextIf = nextIf; } public BooleanCompare getCondition() { return condition; } public ArrayList getStatements() { return statements; } public IfNode getNextIf() { return nextIf; }   @Override public String ToString() { StringBuilder sb = new StringBuilder("IfNode: { Condition: "); sb.append(condition.toString()).append(", Statements: ["); for (StatementNode statement : statements) { sb.append(statement.toString()).append(", "); } sb.delete(sb.length() - 2, sb.length()); sb.append("]"); if (nextIf != null) { sb.append(", NextIf: ").append(nextIf.toString()); } sb.append("}"); return sb.toString(); } } RepeatNode.java import java.util.ArrayList; public class RepeatNode extends Node { private BooleanCompare condition; private ArrayList statements; public RepeatNode(BooleanCompare condition, ArrayList statements) { this.condition = condition; this.statements = statements; } BooleanCompare getCondition() { return condition; } public ArrayList getStatements() { return statements; } @Override public String ToString() { StringBuilder sb = new StringBuilder("RepeatNode: { Condition: "); sb.append(condition.toString()).append(", Statements: ["); for (StatementNode statement : statements) { sb.append(statement.toString()).append(", "); } sb.delete(sb.length() - 2, sb.length()); sb.append("]}"); return sb.toString(); } }   WhileNode.java   import java.util.ArrayList; public class WhileNode extends Node { private BooleanCompare condition; private ArrayList statements; public WhileNode(BooleanCompare condition, ArrayList statements) { this.condition = condition; this.statements = statements; } public BooleanCompare getCondition() { return condition; } public ArrayList getStatements() { return statements; } @Override public String ToString() { StringBuilder sb = new StringBuilder("WhileNode: { Condition: "); sb.append(condition.toString()).append(", Statements: ["); for (StatementNode statement : statements) { sb.append(statement.toString()).append(", "); } sb.delete(sb.length() - 2, sb.length()); sb.append("]}"); return sb.toString(); } }

Java Programming: Below are BooleanCompareNode.java, VariableReferenceNode.java, IfNode.java, RepeatNode.java, & WhileNode.java. Attached is an image where it's circled in blue all the methods that must be implemented in the java files that are presented below:

BooleanCompareNode.java

public class BooleanCompareNode extends Node {
enum CompareType {

eq, ne, lt, gt, le, ge

};

CompareType type;

Node left;

Node right;

public BooleanCompareNode(CompareType type, Node left, Node right) {

this.type = type;

this.left = left;

this.right = right;

}

public String ToString() {

return left.toString() + type.toString() + right.toString();

}

}

VariableReferenceNode.java

public class VariableReferenceNode extends Node{
String name;

Node arrayIndex;

public VariableReferenceNode(String name) {

this.name = name;

this.arrayIndex = arrayIndex;

}

public String ToString() {

String indexString = (arrayIndex == null) ? "" : "[" + arrayIndex.toString() + "]";

return name + indexString;

}

public void setIndex(Node indexExpr) {


}

public String getVariableName() {

return null;
}

}

IfNode.java

import java.util.ArrayList;
import java.util.List;

public class IfNode<BooleanCompare> extends Node{
private BooleanCompare condition;
private ArrayList<StatementNode> statements;
private IfNode nextIf;

public IfNode(BooleanCompare condition, ArrayList<StatementNode> statements, IfNode nextIf) {
this.condition = condition;
this.statements = statements;
this.nextIf = nextIf;
}

public BooleanCompare getCondition() {
return condition;
}

public ArrayList<StatementNode> getStatements() {
return statements;
}

public IfNode getNextIf() {
return nextIf;
}

@Override
public String ToString() {
StringBuilder sb = new StringBuilder("IfNode: { Condition: ");
sb.append(condition.toString()).append(", Statements: [");
for (StatementNode statement : statements) {
sb.append(statement.toString()).append(", ");
}
sb.delete(sb.length() - 2, sb.length());
sb.append("]");
if (nextIf != null) {
sb.append(", NextIf: ").append(nextIf.toString());
}
sb.append("}");
return sb.toString();
}
}

RepeatNode.java

import java.util.ArrayList;

public class RepeatNode<BooleanCompare> extends Node {
private BooleanCompare condition;
private ArrayList<StatementNode> statements;

public RepeatNode(BooleanCompare condition, ArrayList<StatementNode> statements) {
this.condition = condition;
this.statements = statements;
}

BooleanCompare getCondition() {
return condition;
}

public ArrayList<StatementNode> getStatements() {
return statements;
}

@Override
public String ToString() {
StringBuilder sb = new StringBuilder("RepeatNode: { Condition: ");
sb.append(condition.toString()).append(", Statements: [");
for (StatementNode statement : statements) {
sb.append(statement.toString()).append(", ");
}
sb.delete(sb.length() - 2, sb.length());
sb.append("]}");
return sb.toString();
}
}

WhileNode.java

import java.util.ArrayList;

public class WhileNode<BooleanCompare> extends Node {
private BooleanCompare condition;
private ArrayList<StatementNode> statements;

public WhileNode(BooleanCompare condition, ArrayList<StatementNode> statements) {
this.condition = condition;
this.statements = statements;
}

public BooleanCompare getCondition() {
return condition;
}

public ArrayList<StatementNode> getStatements() {
return statements;
}

@Override
public String ToString() {
StringBuilder sb = new StringBuilder("WhileNode: { Condition: ");
sb.append(condition.toString()).append(", Statements: [");
for (StatementNode statement : statements) {
sb.append(statement.toString()).append(", ");
}
sb.delete(sb.length() - 2, sb.length());
sb.append("]}");
return sb.toString();
}
}