String Initialization in Java

String initialization is one of the basic parts of programming. String initialization means assigning a value to the variable before it’s used in the java program. String initialization can be done in two ways:

• Object Initialization
• Direct Initialization

The string is an object in java. String refers to some sequence of the characters.  It’s also known as an array of characters. A String is always indicated in the quotes; even quotes are not part of the String. The string initialization also takes place in two steps, the first one is declaration & the second one is initialization. String declaration refers to declaring a String without assigning any value explicitly. In most of the use cases, the only declaration of the String requires not initialization.

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Types of String Initialization in Java

In java, a String is initialized in multiple ways. Either by using constructor or by using Literal. There is a difference in initializing String by using a new keyword & using Literal. Initializing String using new keywords every time create a new java object. A variable that is defined but not initialized can not be used in the program because it’s not holding any value.

1. Object Initialization

String initialization using the new keyword. Initializing String using a new keyword creates a new object in the heap of memory. String initialized through an object is mutable means to say the value of the string can be reassigned after initialization.

String strMsg = new String("Be specific towards your goal!");

When initiating objects using the constructor, java compilers create a new object in the heap memory. Heap memory is a reserved memory for the JVM.

2. Direct Initialization

String initialization using Literals. String initializing using the Literal creates an object in the pooled area of memory.

String strMsg = "Be specific towards your goal!";

When initializing String using Literal & value assigned to it already initialized in another String. In such a scenario, String created through Literal doesn’t create a new object. It just passed the reference to the earlier created object.

Examples of String Initialization in Java

Following explained are the different examples of string initialization in java.

Example #1

In the below-created String, both the String are created using the Literal.

Code:

String ObjStringFirst="Welcome";
String ObjStringSecond="Welcome";

In the above-given String, we are creating objects using String Literal. In such a situation, if the object is already existing with the same value, it will return the same object; otherwise, it will create a new object.

Example #2

In the below-given example, we can see how Strings are initialized.

Code:

public class StringExample {
public static void main(String[] args)
{
String nameFirst = "Alister";
String nameSecond = "Campbell";
String nameThird = new String("Adam");
String nameFourth = new String("Martin");
//String nameFifth;
String strNullFirst  = null;
String strNullSecond = null;
String strNullThird  = null;
System.out.println("String initialized :");
//printing variable which are initialized
System.out.println("First : " + nameFirst);
System.out.println("Second : " + nameSecond);
System.out.println("Third : " + nameThird);
//printing variable which are declared but not initialized
//System.out.println("String declared but not initialized :");
//System.out.println("Fifth : " + nameFifth);
}
}

Output:

Example #3

In this example, a declaration of the String variable is given. It contains a variable that is declared but not initialized on compiling the program.

Code:

public class StringExample {
public static void main(String[] args)
{
String nameFirst;
//printing variable which are declared but not initialized
System.out.println("String declared but not initialized :");
System.out.println("Fifth : " + nameFirst);
}
}

Output:

The output of the above program is given below. The above-given program will generate the error on compilation. The string is declared but not initialized.

After the String declaration, if any value is assigned later for the declared String variable, then compilation will not throw any error (as String initialization takes in two parts). The first one is declaration & the second one is an assignment.

Example #4

In this example, let’s go with the String initialization with empty values. All the String variables initiated through empty values will have different objects for all three as String initialized through Literal will create an Object in the String pool while String initialized through new keyword will create objects in the heap area of memory.

Code:

public class StringExample {
public static void main(String[] args)
{
String strVal1 = "";
String strVal2 = new String();
String strVal3 = new String("");
//printing variable which are initialized with empty values
System.out.println("String Values :");
System.out.println("First : " + strVal1);
System.out.println("Second : " + strVal2);
System.out.println("Third : " + strVal3);
}
}

Output:

In the above-given program, even the object for Strings is different, but the value assigned to the String is the same. Below given output shows how empty values are assigned to each String variable.

Example #5

In the below-given program, a comparison of the above-initialized strings is given. Using here three-way of comparing the String.

1. == operator: In java == operator compare the references, not the values.
2. equals() method: It compares the variable’s value, not the references; hence, if the value matches both the String variable, it returns true other false.
3. compareTo() method: compareTo() method check the values & if values are identical then it return 0 otherwise it return + & – based on the below given comparison.

• It returns 0 if str1 == str2
• It returns positive value if str1 > str2
• It returns negative value if str1 < str2

Code:

public class StringExample {
public static void main(String[] args)
{
String strVal1 = "";
String strVal2 = new String();
String strVal3 = new String("");
//printing variable which are initialized with empty values
System.out.println("String Values :");
System.out.println("First : " + strVal1);
System.out.println("Second : " + strVal2);
System.out.println("Third : " + strVal3);
System.out.println(" \nComparing strings using == operator :");
System.out.println("Comparing first two strings :");
System.out.println(strVal1 == strVal2);
System.out.println("Comparing last two strings :");
System.out.println(strVal2 == strVal3);
System.out.println("Comparing first & last strings :");
System.out.println(strVal1 == strVal3);
System.out.println(" \nComparing strings using equals method :");
System.out.println("Comparing first two strings :");
System.out.println(strVal1.equals(strVal2));
System.out.println("Comparing last two strings :");
System.out.println(strVal2.equals(strVal3));
System.out.println("Comparing first & last strings :");
System.out.println(strVal1.equals(strVal3));
System.out.println(" \nComparing strings using compareTo method :");
System.out.println("Comparing first two strings :");
System.out.println(strVal1.compareTo(strVal2));
System.out.println("Comparing last two strings :");
System.out.println(strVal2.compareTo(strVal3));
System.out.println("Comparing first & last strings :");
System.out.println(strVal1.compareTo(strVal3));
}
}

Output:

The output of the comparing string program is given below. It contains the output after comparing the Strings in three different ways; thus, outcomes of the comparison are also different according to the method applied.

Conclusion

The above-given article explains the initialization of String & different types of ways to initialize the String in java. Also given examples in the article describe the internal creation of objects when initiating String using Literal. It also describes the difference between declaration & initialization.

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