Please explain Common String Mistake in the code below/question in Bold: public class StringMistakeDemo { public static void main(String[] args) { String a = "Roux"; String b = "Roux"; String c = new String("Roux"); /* * Number 1 * Consider the output from the this block of code. * Which line causes the "false"? * Why are the last two lines different? / System.out.println(); System.out.println("Roux" == "Roux"); //comparing two strings System.out.println(a == b); //comparing two string variables System.out.println(a == c); //comparing two other string variables System.out.println(a.equals(c));//using the string class method "equals" / * Number 2 * "identityHashCode" provides a numeric signature that includes the * memory location for the variable. * What does the following output tell you about how Java stores strings? / System.out.println(); System.out.println(Integer.toHexString(System.identityHashCode(a))); System.out.println(Integer.toHexString(System.identityHashCode(b))); System.out.println(Integer.toHexString(System.identityHashCode(c))); / * Number 3 * What happens in memory when you modify the string? / System.out.println(); a = a + b; System.out.println(a); System.out.println(Integer.toHexString(System.identityHashCode(a))); System.out.println(Integer.toHexString(System.identityHashCode(b))); System.out.println(Integer.toHexString(System.identityHashCode(c))); / * Number 4 * When would you use the equality operator "==" and .equals? */ } }

Database System Concepts

7th Edition

ISBN:9780078022159

Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Chapter1: Introduction

Section: Chapter Questions

Problem 1PE

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Question

Please explain Common String Mistake in the code below/question in Bold:

public class StringMistakeDemo
{
public static void main(String[] args) {
String a = "Roux";
String b = "Roux";
String c = new String("Roux");

/*
* Number 1
* Consider the output from the this block of code.
* Which line causes the "false"?
* Why are the last two lines different?
*/

System.out.println();
System.out.println("Roux" == "Roux"); //comparing two strings
System.out.println(a == b); //comparing two string variables
System.out.println(a == c); //comparing two other string variables
System.out.println(a.equals(c));//using the string class method "equals"

/*
* Number 2
* "identityHashCode" provides a numeric signature that includes the
* memory location for the variable.
* What does the following output tell you about how Java stores strings?
*/

System.out.println();
System.out.println(Integer.toHexString(System.identityHashCode(a)));
System.out.println(Integer.toHexString(System.identityHashCode(b)));
System.out.println(Integer.toHexString(System.identityHashCode(c)));

/*
* Number 3
* What happens in memory when you modify the string?
*/

System.out.println();
a = a + b;
System.out.println(a);
System.out.println(Integer.toHexString(System.identityHashCode(a)));
System.out.println(Integer.toHexString(System.identityHashCode(b)));
System.out.println(Integer.toHexString(System.identityHashCode(c)));

/*
* Number 4
* When would you use the equality operator "==" and .equals?
*/
}
}