Java String startsWith()

The Java String class startsWith() method checks if this string starts with the given prefix. It returns true if this string starts with the given prefix; else returns false.

Signature

The syntax or signature of startWith() method is given below.

public boolean startsWith(String prefix)
public boolean startsWith(String prefix, int offset)

Parameter

prefix : Sequence of character

offset: the index from where the matching of the string prefix starts.

Returns

true or false

Internal implementation of startsWith(String prefix, int toffset)

public boolean startsWith(String prefix, int toffset) {  
     char ta[] = value;  
     int to = toffset;  
     char pa[] = prefix.value;  
     int po = 0;  
     int pc = prefix.value.length;  
     // Note: toffset might be near -1>>>1.  
     if ((toffset < 0) || (toffset > value.length - pc)) {  
         return false;  
     }  
     while (--pc >= 0) {  
         if (ta[to++] != pa[po++]) {  
             return false;  
         }  
     }  
     return true;  
 }  

Internal Implementation of startsWith(String prefix,)

// Since the offset is not mentioned in this type of startWith() method, the offset is
// considered as 0.
public boolean startsWith(String prefix) 
{
// the offset is 0
return startsWith(prefix, 0);
}

Java String startsWith() method example

The startsWith() method considers the case-sensitivity of characters. Consider the following example.

FileName: StartsWithExample.java

public class StartsWithExample
{  
// main method
public static void main(String args[])
{  
// input string
String s1="java string split method by javatpoint";  
System.out.println(s1.startsWith("ja"));  // true
System.out.println(s1.startsWith("java string"));   // true
System.out.println(s1.startsWith("Java string"));  // false as 'j' and 'J' are different 
}
}  

Output:

true
true
false

Java String startsWith(String prefix, int offset) Method Example

It is an overloaded method of the startWith() method that is used to pass an extra argument (offset) to the function. The method works from the passed offset. Let's see an example.

FileName: StartsWithExample2.java

public class StartsWithExample2 {  
    public static void main(String[] args) {  
        String str = "Javatpoint";  
        // no offset mentioned; hence, offset is 0 in this case.
        System.out.println(str.startsWith("J")); // True  

         // no offset mentioned; hence, offset is 0 in this case.
        System.out.println(str.startsWith("a")); // False 
        // offset is 1
        System.out.println(str.startsWith("a",1)); // True  
    }  
}  

Output:

true
false
true

Java String startsWith() Method Example - 3

If we adding an empty string at the beginning of a string, then it has no impact at all on the string.

"" + "Tokyo Olympics" = "Tokyo Olympics"s

It means one can say that a string in Java always starts with the empty string. Let's confirm the same with the help of Java code.

FileName: StartsWithExample3.java

public class StartsWithExample3 
{
// main method
public static void main(String argvs[])
{
// input string
String str = "Tokyo Olympics";

if(str.startsWith(""))
{
System.out.println("The string starts with the empty string.");
}
else
{
System.
out.println("The string does not start with the empty string.");   
}

}
}

Output:

The string starts with the empty string.

Next TopicJava String substring()

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Java String startsWith()

Signature

Parameter

Returns

Internal implementation of startsWith(String prefix, int toffset)

Internal Implementation of startsWith(String prefix,)

Java String startsWith() method example

Java String startsWith(String prefix, int offset) Method Example

Java String startsWith() Method Example - 3