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iluwatar#107 Interpreter example JavaDoc
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7 files changed

+220
-186
lines changed

7 files changed

+220
-186
lines changed

‎interpreter/src/main/java/com/iluwatar/interpreter/App.java‎

Lines changed: 72 additions & 68 deletions
Original file line numberDiff line numberDiff line change
@@ -1,68 +1,72 @@
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package com.iluwatar.interpreter;
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import java.util.Stack;
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/**
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*
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* Interpreter pattern breaks sentences into expressions (Expression) that can
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* be evaluated and as a whole form the result.
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*
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*/
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public class App {
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/**
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*
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* Expressions can be evaluated using prefix, infix or postfix notations
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* This sample uses postfix, where operator comes after the operands
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*
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*/
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public static void main(String[] args) {
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String tokenString = "4 3 2 - 1 + *";
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Stack<Expression> stack = new Stack<>();
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String[] tokenList = tokenString.split(" ");
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for (String s : tokenList) {
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if (isOperator(s)) {
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Expression rightExpression = stack.pop();
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Expression leftExpression = stack.pop();
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System.out
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.println(String.format(
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"popped from stack left: %d right: %d",
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leftExpression.interpret(),
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rightExpression.interpret()));
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Expression operator = getOperatorInstance(s, leftExpression,
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rightExpression);
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System.out.println(String.format("operator: %s", operator));
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int result = operator.interpret();
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NumberExpression resultExpression = new NumberExpression(result);
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stack.push(resultExpression);
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System.out.println(String.format("push result to stack: %d",
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resultExpression.interpret()));
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} else {
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Expression i = new NumberExpression(s);
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stack.push(i);
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System.out.println(String.format("push to stack: %d",
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i.interpret()));
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}
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}
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System.out
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.println(String.format("result: %d", stack.pop().interpret()));
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}
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public static boolean isOperator(String s) {
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return s.equals("+") || s.equals("-") || s.equals("*");
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}
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public static Expression getOperatorInstance(String s, Expression left,
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Expression right) {
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switch (s) {
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case "+":
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return new PlusExpression(left, right);
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case "-":
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return new MinusExpression(left, right);
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case "*":
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return new MultiplyExpression(left, right);
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}
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return null;
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}
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}
1+
package com.iluwatar.interpreter;
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3+
import java.util.Stack;
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/**
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*
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* Interpreter pattern breaks sentences into expressions ({@link Expression}) that can
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* be evaluated and as a whole form the result.
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*
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*/
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public class App {
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/**
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*
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* Program entry point.
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* <p>
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* Expressions can be evaluated using prefix, infix or postfix notations
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* This sample uses postfix, where operator comes after the operands
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*
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* @param args command line args
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*
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*/
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public static void main(String[] args) {
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String tokenString = "4 3 2 - 1 + *";
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Stack<Expression> stack = new Stack<>();
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String[] tokenList = tokenString.split(" ");
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for (String s : tokenList) {
29+
if (isOperator(s)) {
30+
Expression rightExpression = stack.pop();
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Expression leftExpression = stack.pop();
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System.out
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.println(String.format(
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"popped from stack left: %d right: %d",
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leftExpression.interpret(),
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rightExpression.interpret()));
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Expression operator = getOperatorInstance(s, leftExpression,
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rightExpression);
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System.out.println(String.format("operator: %s", operator));
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int result = operator.interpret();
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NumberExpression resultExpression = new NumberExpression(result);
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stack.push(resultExpression);
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System.out.println(String.format("push result to stack: %d",
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resultExpression.interpret()));
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} else {
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Expression i = new NumberExpression(s);
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stack.push(i);
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System.out.println(String.format("push to stack: %d",
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i.interpret()));
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}
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}
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System.out
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.println(String.format("result: %d", stack.pop().interpret()));
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}
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public static boolean isOperator(String s) {
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return s.equals("+") || s.equals("-") || s.equals("*");
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}
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public static Expression getOperatorInstance(String s, Expression left,
61+
Expression right) {
62+
switch (s) {
63+
case "+":
64+
return new PlusExpression(left, right);
65+
case "-":
66+
return new MinusExpression(left, right);
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case "*":
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return new MultiplyExpression(left, right);
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}
70+
return null;
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}
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}

‎interpreter/src/main/java/com/iluwatar/interpreter/Expression.java‎

Lines changed: 14 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -1,9 +1,14 @@
1-
package com.iluwatar.interpreter;
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public abstract class Expression {
4-
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public abstract int interpret();
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@Override
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public abstract String toString();
9-
}
1+
package com.iluwatar.interpreter;
2+
3+
/**
4+
*
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* Expression
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*
7+
*/
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public abstract class Expression {
9+
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public abstract int interpret();
11+
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@Override
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public abstract String toString();
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}

‎interpreter/src/main/java/com/iluwatar/interpreter/MinusExpression.java‎

Lines changed: 28 additions & 23 deletions
Original file line numberDiff line numberDiff line change
@@ -1,23 +1,28 @@
1-
package com.iluwatar.interpreter;
2-
3-
public class MinusExpression extends Expression {
4-
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private Expression leftExpression;
6-
private Expression rightExpression;
7-
8-
public MinusExpression(Expression leftExpression, Expression rightExpression) {
9-
this.leftExpression = leftExpression;
10-
this.rightExpression = rightExpression;
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}
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@Override
14-
public int interpret() {
15-
return leftExpression.interpret() - rightExpression.interpret();
16-
}
17-
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@Override
19-
public String toString() {
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return "-";
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}
22-
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}
1+
package com.iluwatar.interpreter;
2+
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/**
4+
*
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* MinusExpression
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*
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*/
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public class MinusExpression extends Expression {
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private Expression leftExpression;
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private Expression rightExpression;
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public MinusExpression(Expression leftExpression, Expression rightExpression) {
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this.leftExpression = leftExpression;
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this.rightExpression = rightExpression;
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}
17+
18+
@Override
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public int interpret() {
20+
return leftExpression.interpret() - rightExpression.interpret();
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}
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23+
@Override
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public String toString() {
25+
return "-";
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}
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}

‎interpreter/src/main/java/com/iluwatar/interpreter/MultiplyExpression.java‎

Lines changed: 29 additions & 24 deletions
Original file line numberDiff line numberDiff line change
@@ -1,24 +1,29 @@
1-
package com.iluwatar.interpreter;
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public class MultiplyExpression extends Expression {
4-
5-
private Expression leftExpression;
6-
private Expression rightExpression;
7-
8-
public MultiplyExpression(Expression leftExpression,
9-
Expression rightExpression) {
10-
this.leftExpression = leftExpression;
11-
this.rightExpression = rightExpression;
12-
}
13-
14-
@Override
15-
public int interpret() {
16-
return leftExpression.interpret() * rightExpression.interpret();
17-
}
18-
19-
@Override
20-
public String toString() {
21-
return "*";
22-
}
23-
24-
}
1+
package com.iluwatar.interpreter;
2+
3+
/**
4+
*
5+
* MultiplyExpression
6+
*
7+
*/
8+
public class MultiplyExpression extends Expression {
9+
10+
private Expression leftExpression;
11+
private Expression rightExpression;
12+
13+
public MultiplyExpression(Expression leftExpression,
14+
Expression rightExpression) {
15+
this.leftExpression = leftExpression;
16+
this.rightExpression = rightExpression;
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}
18+
19+
@Override
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public int interpret() {
21+
return leftExpression.interpret() * rightExpression.interpret();
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}
23+
24+
@Override
25+
public String toString() {
26+
return "*";
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}
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}

‎interpreter/src/main/java/com/iluwatar/interpreter/NumberExpression.java‎

Lines changed: 30 additions & 25 deletions
Original file line numberDiff line numberDiff line change
@@ -1,25 +1,30 @@
1-
package com.iluwatar.interpreter;
2-
3-
public class NumberExpression extends Expression {
4-
5-
private int number;
6-
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public NumberExpression(int number) {
8-
this.number = number;
9-
}
10-
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public NumberExpression(String s) {
12-
this.number = Integer.parseInt(s);
13-
}
14-
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@Override
16-
public int interpret() {
17-
return number;
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}
19-
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@Override
21-
public String toString() {
22-
return "number";
23-
}
24-
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}
1+
package com.iluwatar.interpreter;
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/**
4+
*
5+
* NumberExpression
6+
*
7+
*/
8+
public class NumberExpression extends Expression {
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private int number;
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public NumberExpression(int number) {
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this.number = number;
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}
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public NumberExpression(String s) {
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this.number = Integer.parseInt(s);
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}
19+
20+
@Override
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public int interpret() {
22+
return number;
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}
24+
25+
@Override
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public String toString() {
27+
return "number";
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}
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}

‎interpreter/src/main/java/com/iluwatar/interpreter/PlusExpression.java‎

Lines changed: 28 additions & 23 deletions
Original file line numberDiff line numberDiff line change
@@ -1,23 +1,28 @@
1-
package com.iluwatar.interpreter;
2-
3-
public class PlusExpression extends Expression {
4-
5-
private Expression leftExpression;
6-
private Expression rightExpression;
7-
8-
public PlusExpression(Expression leftExpression, Expression rightExpression) {
9-
this.leftExpression = leftExpression;
10-
this.rightExpression = rightExpression;
11-
}
12-
13-
@Override
14-
public int interpret() {
15-
return leftExpression.interpret() + rightExpression.interpret();
16-
}
17-
18-
@Override
19-
public String toString() {
20-
return "+";
21-
}
22-
23-
}
1+
package com.iluwatar.interpreter;
2+
3+
/**
4+
*
5+
* PlusExpression
6+
*
7+
*/
8+
public class PlusExpression extends Expression {
9+
10+
private Expression leftExpression;
11+
private Expression rightExpression;
12+
13+
public PlusExpression(Expression leftExpression, Expression rightExpression) {
14+
this.leftExpression = leftExpression;
15+
this.rightExpression = rightExpression;
16+
}
17+
18+
@Override
19+
public int interpret() {
20+
return leftExpression.interpret() + rightExpression.interpret();
21+
}
22+
23+
@Override
24+
public String toString() {
25+
return "+";
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}
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}

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