Different output without the parantheses

[Loganathan Karunakaran]

Please refer the below two programs:

1)

class StringTest2{
	public static void main(String... args){
		String a = new String("abc");
		String b = "abc";
		String c = "abc";
		System.out.println("a==b " + a==b );
		System.out.println("b==c " + b==c );
		System.out.println("a==c " + a==c );
	}
}

Output:

false
false
false

2)

class StringTest2{
	public static void main(String... args){
		String a = new String("abc");
		String b = "abc";
		String c = "abc";
		System.out.println("a==b " + (a==b));
		System.out.println("b==c " + (b==c));
		System.out.println("a==c " + (a==c));
	}
}

output

a==b false
b==c true
a==c false

For the second program I get the output as expected. Here b==c is true

wherease for the first program, I have not given the parantheses, the results vary. I am not getting whatever I given in the double quotes. Also I expect b==c to be true, but it prints as false.

Please help me to understand how the parantheses play the role to get different outputs here.

[Ikpefua Jacob-Obinyan]

Hello Loganathan...Please use code tags in other to make your programs easier to read.

class StringTest2{
public static void main(String... args){
String a = new String("abc");
String b = "abc";
String c = "abc";
System.out.println("a==b " + a==b );
System.out.println("b==c " + b==c );
System.out.println("a==c " + a==c );
}
} 

Output

false
false
false 

class StringTest2{
public static void main(String... args){
String a = new String("abc");
String b = "abc";
String c = "abc";
System.out.println("a==b " + (a==b));
System.out.println("b==c " + (b==c));
System.out.println("a==c " + (a==c));
}
} 

Output

a==b false
b==c true
a==c false 

[Ikpefua Jacob-Obinyan]

Loganathan, the pritnln statement in your first program is carrying out string concatenation (adding "b==c" to the value of 'b' which evaluates to "b==cabc" and comparing the result to 'c' ) that is why the output is different, with this:

System.out.println(a==b);
System.out.println(b==c);
System.out.println(a==c);

The output will be as expected:

false
true
false

Always watchout for 'String Concatenation'.

Regards

Ikpefua.

[Loganathan Karunakaran]

Hi Ikpefua,

Thanks for your time and explanation. I understood the difference. Here the operator precedence comes into the rule without the parantheses. The + operator has higher precedence than the == operator. Thanks a lot.

Regards
Loganathan