update 1

Author: Azo-hub

.classpath

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<classpath>
+	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-17">
+		<attributes>
+			<attribute name="module" value="true"/>
+		</attributes>
+	</classpathentry>
+	<classpathentry kind="src" path="src"/>
+	<classpathentry kind="output" path="bin"/>
+</classpath>

.project

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+<?xml version="1.0" encoding="UTF-8"?>
+<projectDescription>
+	<name>coreJavaPractice</name>
+	<comment></comment>
+	<projects>
+	</projects>
+	<buildSpec>
+		<buildCommand>
+			<name>org.eclipse.jdt.core.javabuilder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
+	</buildSpec>
+	<natures>
+		<nature>org.eclipse.jdt.core.javanature</nature>
+	</natures>
+</projectDescription>

.settings/org.eclipse.core.resources.prefs

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+eclipse.preferences.version=1
+encoding/<project>=UTF-8

.settings/org.eclipse.jdt.core.prefs

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+eclipse.preferences.version=1
+org.eclipse.jdt.core.compiler.codegen.inlineJsrBytecode=enabled
+org.eclipse.jdt.core.compiler.codegen.targetPlatform=17
+org.eclipse.jdt.core.compiler.codegen.unusedLocal=preserve
+org.eclipse.jdt.core.compiler.compliance=17
+org.eclipse.jdt.core.compiler.debug.lineNumber=generate
+org.eclipse.jdt.core.compiler.debug.localVariable=generate
+org.eclipse.jdt.core.compiler.debug.sourceFile=generate
+org.eclipse.jdt.core.compiler.problem.assertIdentifier=error
+org.eclipse.jdt.core.compiler.problem.enablePreviewFeatures=disabled
+org.eclipse.jdt.core.compiler.problem.enumIdentifier=error
+org.eclipse.jdt.core.compiler.problem.reportPreviewFeatures=warning
+org.eclipse.jdt.core.compiler.release=enabled
+org.eclipse.jdt.core.compiler.source=17

bin/coreJavaPractice/Main.class

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+package coreJavaPractice;
+
+import java.util.Stack;
+
+/**
+ * @author Azo-hub
+ * @github (https://github.com/Azo-hub)
+ * @since 2020
+ */
+public class Main {
+	
+	public static void main(String [] args) {
+		/* Reverse Polish Notation
+		 * ["2", "1", "+", "3", "*"] => ((2 + 1) * 3) => 9 
+		 * ["4", "13", "5", "/", "+"] => (4 + (13 / 5)) => 6
+		 */
+		
+		String[] tokens = {"4", "13", "5", "/", "+"};
+		System.out.println(evalRPN(tokens));
+		
+	}
+	
+	public static int evalRPN(String[] tokens) {
+		
+		int returnValue = 0;
+		String operators = "+-*/";
+		
+		Stack<String> stack = new Stack<>();
+		
+		for(String t : tokens) {
+			
+			if(!operators.contains(t)) {
+				stack.push(t);
+			} else {
+				
+				int a = Integer.valueOf(stack.pop());
+				int b = Integer.valueOf(stack.pop());
+				
+				/* System.out.print("a: " + a + "and b: " + b); */
+				
+				switch(t) {
+				
+				case "+":
+					stack.push(String.valueOf(b + a));
+					break;
+					
+				case "-":
+					stack.push(String.valueOf(b - a));
+					break;
+					
+				case "*":
+					stack.push(String.valueOf(b * a));
+					break;
+					
+				case "/":
+					stack.push(String.valueOf(b / a));
+					break;
+					
+				}
+			}
+		}
+		
+		returnValue = Integer.valueOf(stack.pop());
+		
+		return returnValue;
+	}
+	
+	
+}
+
+
+

bin/module-info.class

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+/**
+ * @author dell
+ *
+ */
+module coreJavaPractice {
+}