CODEWITHSUNDEEP
javasubstringequals
Trịnh Vũ Long
Trịnh Vũ Long

Reputation: 11

equals() method return false when comparing between a subString and a String array's element

I made a simple code like below and I can't understand why it's false when comparing between a subString and a String array's element.

public static void main(String[] args) {
    String str = "abcdef";
    String str1 = str.substring(0, 4);
    String str2 = "abcd";

    String[]arr = new String [10];
    System.out.println(arr [0 ]+ " - " + str1);                 //output: null - abcd
    arr[0] = str1;
    System.out.println("after: " +  arr [0] + " - " + str1);    //output: after: abcd - abcd

    boolean b = str.equals(arr[0]);
    System.out.println(b);                                      //output: false
    System.out.println(str1.equals(str2));                      //output: true

    System.out.println(str1.length() +  " " + str2.length() + " " + arr[0].length()); //output: 4 4 4
}

str1, str2, arr[0]: they are same in length and character, but the compare's result is difference. that's weird. anyone can know about it, pls share.

Upvotes: 0

Views: 90

Answers (2)

umop apisdn
umop apisdn

Reputation: 683

Over here, you are comparing:

    boolean b = str.equals(arr[0]);

but str is abcdef while arr[0] is str1 which is abcd. Hence they are not equal.

Upvotes: 2

Tom Hawtin - tackline
Tom Hawtin - tackline

Reputation: 147124

boolean b = str.equals(arr[0]);

Did you mean

boolean b = str1.equals(arr[0]);

or

boolean b = str2.equals(arr[0]);

Or did you think that 

String str1 = str.substring(0, 4);

modifies str?

Upvotes: 0

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