Comparing Two String Objects in Java

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String class provides equals method for comparing two String objects.

Comparing two String variables:

String str1 = "Java";
String str2 = "Java";
if(str1.equals(str2)) {
	System.out.println("str1 and str2 are equal");
} else {
	System.out.println("str1 and str2 are not equal");
}

Output:

str1 and str2 are equal

However, this may result in NullPointerException if str1 is null. So, it is always better to check if the reference variable is not null, which is calling the equals method.

String str1 = null;
String str2 = "Java";
if (str1 != null && str1.equals(str2)) {
	System.out.println("str1 and str2 are equal");
} else {
	System.out.println("str1 and str2 are not equal");
}

Output:

str1 and str2 are not equal

You don’t have to null check for the variable that is being passed into equals method.

String str1 = "Java";
String str2 = null;
if (str1 != null && str1.equals(str2)) {
	System.out.println("str1 and str2 are equal");
} else {
	System.out.println("str1 and str2 are not equal");
}

Comparing String variable with String literal

String str1 = "Java";
if ("Java".equals(str1)) {
	System.out.println("str1 and str2 are equal");
} else {
	System.out.println("str1 and str2 are not equal");
}

Since, String literal “Java” is also a String object, you can call String methods on it. This style of comparison avoids null check for the String variable.

Check for String inequality

String str1 = "Java";
if (!"Oracle".equals(str1)) {
	System.out.println("str1 and str2 are not equal");
} else {
	System.out.println("str1 and str2 are equal");
}

Ignore case while comparing

String str1 = "Java";
if ("JAVA".equalsIgnoreCase(str1)) {
	System.out.println("str1 and str2 are equal");
} else {
	System.out.println("str1 and str2 are not equal");
}

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