CODEWITHSUNDEEP
javaarrayspass-by-referencepass-by-value
Rose
Rose

Reputation: 57

What's the deal with object array in java?

I know java is pass by value, period. However, I still can't figure out this.

public static void changeTheName(String obj){
 obj.toUpperCase();
}

This method will not affect the original string object, Fairly understandable. Because strings are immutable and changing in string literals means that the reference variable will now refer to the new object and the old one will be left for the garbage collector. But when I pass a string array I'm able to change the string literals that means I'm able to change the references. Why is this happening with the array because if we do obj[]= new String[]{} it will not affect to the original array and the original still refers to the old array and that is similar to directly changing the string literals

public static void ChangeTheName(String obj[]){
 for(int i=0;i<obj.length();i++) obj[i]=obj[i].toUpperCase;
}

Edit: The answer I was looking for is that reference of obj and obj[0] are unique and that's why the second method is able to change the entire content of my array. As I'm from C background and I thought obj and obj[0] has same refernces but that is not the case in java for sure.

Upvotes: 0

Views: 90

Answers (3)

SSP
SSP

Reputation: 2670

@karthikdivi said - toUpperCase() does not change the String. it returns a new String which is uppercase.

But as i understand that you want to know why object value is changed in method but not premitive data type value?

Although Java is strictly pass by value, the precise effect differs between whether a primitive type or a reference type is passed.

.

When we pass a primitive type to a method, it is passed by value. But when we pass an object to a method, the situation changes dramatically, because objects are passed by what is effectively call-by-reference. Java does this interesting thing that’s sort of a hybrid between pass-by-value and pass-by-reference. Basically, a parameter cannot be changed by the function, but the function can ask the parameter to change itself via calling some method within it.

While creating a variable of a class type, we only create a reference to an object. Thus, when we pass this reference to a method, the parameter that receives it will refer to the same object as that referred to by the argument.

This effectively means that objects act as if they are passed to methods by use of call-by-reference.

Changes to the object inside the method do reflect in the object used as an argument.

Upvotes: 1

Pranav MS
Pranav MS

Reputation: 2296

if you are doing like below will only change the value.

public static void(String obj[]){
 for(String s:obj) {
   s=s.toUpperCase();
  }
}

I think thus make changes.

Upvotes: 0

karthikdivi
karthikdivi

Reputation: 3633

toUpperCase does not change the String, it returns a new String which is uppercase.

Upvotes: 1

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