What s the difference between equals and

Question

I switched lecturers today and he stated using a weird code to me   He said it s better to use  equals and when I asked why  he answered  because it is     So here s an example   if  o1 equals o2      System out println  Both integer objects are the same        Instead of what I m used to   if  o1    o2      System out println  Both integer objects are the same        What s the difference between the two  And why is his way  using  equals  better   Found this on a quick search but I can t really make sense of that answer

User · Answer

Here is a simple interpretation about your problem:

== (equal to) used to evaluate arithmetic expression

where as

equals() method used to compare string

Therefore, it its better to use == for numeric operations & equals() method for String related operations. So, for comparison of objects the equals() method would be right choice.

User · Answer

Lets say that      operator returns true if both both operands belong to same object but when it will return true as we can t assign a single object multiple values  public static void main String    args       String s1    Hello       String s1    Hello       This is not possible to assign multiple values to single object     if s1    s1            Now this retruns true          Now when this happens practically speaking  If its not happen then why this is    compares functionality

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1     can be be applied for both primitives and object types  but equals   method can be applied for only object types    2     cannot be overridden for content comparison  but equals method can be overridden for content comparison ex  String class  wrapper classes  collection classes     3     gives incomparable types error when try to apply for heterogeneous types   where as equals method returns false

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In Java  when the          operator is used to compare 2 objects  it checks to see if the objects refer to the same place in memory  EX   String obj1   new String  xyz    String obj2   new String  xyz    if obj1    obj2     System out println  obj1  obj2 is TRUE    else   System out println  obj1  obj2 is FALSE      Even though the strings have the same exact characters     xyz      The code above will actually output   obj1  obj2 is FALSE  Java String class actually overrides the default equals   implementation in the Object class     and it overrides the method so that it checks only the values of the strings  not their locations in memory  This means that if you call the equals   method to compare 2 String objects  then as long as the actual sequence of characters is equal  both objects are considered equal    String obj1   new String  xyz    String obj2   new String  xyz    if obj1 equals obj2      System out printlln  obj1  obj2 is TRUE    else   System out println  obj1  obj2 is FALSE      This code will output the following   obj1  obj2 is TRUE

User · Answer

The    operator compares if the objects are the same instance  The equals   oerator compares the state of the objects  e g  if all attributes are equal   You can even override the equals   method to define yourself when an object is equal to another

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In Java     always just compares two references  for non-primitives  that is  - i e  it tests whether the two operands refer to the same object   However  the equals method can be overridden - so two distinct objects can still be equal   For example   String x    hello   String y   new String new char      h    e    l    l    o       System out println x    y      false System out println x equals y       true   Additionally  it s worth being aware that any two equal string constants  primarily string literals  but also combinations of string constants via concatenation  will end up referring to the same string  For example   String x    hello   String y    he     llo   System out println x    y      true    Here x and y are references to the same string  because y is a compile-time constant equal to  hello

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public static void main String   args           String s1   new String  hello            String s2   new String  hello             System out println s1 equals s2                         System out println s1    s2        System out println  -----------------------------             String s3    hello           String s4    hello            System out println s3 equals s4                         System out println s3    s4           Here in this code u can campare the both      and   equals   here  equals is used to compare the reference objects and      is used to compare state of objects

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If you and I each walk into the bank  each open a brand new account  and each deposit  100  then      myAccount equals yourAccount  is true because they have the same value  but myAccount    yourAccount is false because they are not the same account     Assuming appropriate definitions of the Account class  of course   -

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operator compares two object references to check whether they refer to same instance  This also  will return true on successful match for example  public class Example  public static void main String   args   String s1    Java   String s2    Java   String s3   new string   Java    test Sl    s2        true test s1    s3         false      above example     is a reference comparison i e  both objects point to the same memory location  String equals   is  evaluates to the comparison of values in the objects      public class EqualsExample1     public static void main String args        String s    Hell      String s1  new string   Hello       String s2  new string   Hello       s1 equals s2        true     s equals s1        false          above  example It compares the content of the strings  It will return true if string matches  else returns false

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is an operator  equals is a method defined in the Object class     checks if two objects have the same address in the memory and for primitive it checks if they have the same value equals method on the other hand checks if the two objects which are being compared have an equal value depending on how ofcourse the equals method has been implemented for the objects  equals method cannot be applied on primitives which means that  if a is a primitive a equals someobject  is not allowed  however someobject equals a  is allowed

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The equals    method and the    operator perform two different operations  The equals    method compares the characters inside a String object  The    operator compares two object references to see whether they refer to the same instance  The following program shows how two different String objects can contain the same characters  but references to these objects will not compare as equal      equals   vs    class EqualsNotEqualTo        public static void main String args                String s1    Hello             String s2   new String s1             System out println s1     equals     s2     - gt                s1 equals s2              System out println s1            s2     - gt       s1    s2               The variable s1 refers to the String instance created by    Hello     The object referred to by s2 is created with s1 as an initializer  Thus  the contents of the two String objects are identical  but they are distinct objects  This means that s1 and s2 do not refer to the same objects and are  therefore  not     as is shown here by the output of the preceding example   Hello equals Hello - gt  true Hello    Hello - gt  false

[java] What's the difference between ".equals" and "=="?

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