Java
Java Strings
String vs StringBuffer

Difference Between String and StringBuffer

No.StringStringBuffer
1The String class is immutable.The StringBuffer class is mutable.
2String is slow and consumes more memory when we concatenate too many strings because every time it creates a new instance.StringBuffer is fast and consumes less memory when concatenating strings.
3String class overrides the equals() method of Object class, allowing content comparison.StringBuffer class doesn't override the equals() method.
4String class is slower while performing concatenation operations.StringBuffer class is faster while performing concatenation operations.
5String class uses the String constant pool.StringBuffer uses heap memory.

Performance Test of String and StringBuffer

public class ConcatTest {  
    public static String concatWithString() {  
        String t = "Coding";  
        for (int i = 0; i < 10000; i++) {  
            t = t + "75";  
        }  
        return t;  
    }  
    public static String concatWithStringBuffer() {  
        StringBuffer sb = new StringBuffer("Coding");  
        for (int i = 0; i < 10000; i++) {  
            sb.append("75");  
        }  
        return sb.toString();  
    }  
    public static void main(String[] args) {  
        long startTime = System.currentTimeMillis();  
        concatWithString();  
        System.out.println("Time taken by Concatenating with String: " + (System.currentTimeMillis() - startTime) + "ms");  
        startTime = System.currentTimeMillis();  
        concatWithStringBuffer();  
        System.out.println("Time taken by Concatenating with StringBuffer: " + (System.currentTimeMillis() - startTime) + "ms");  
    }  
}

Output:

Time taken by Concatenating with String: 578ms
Time taken by Concatenating with StringBuffer: 0ms

String and StringBuffer HashCode Test

public class InstanceTest {  
    public static void main(String args[]) {  
        System.out.println("Hashcode test of String:");  
        String str = "coding";  
        System.out.println(str.hashCode());  
        str = str + "75";  
        System.out.println(str.hashCode());  
   
        System.out.println("Hashcode test of StringBuffer:");  
        StringBuffer sb = new StringBuffer("coding");  
        System.out.println(sb.hashCode());  
        sb.append("75");  
        System.out.println(sb.hashCode());  
    }  
}

Output:

Hashcode test of String:
3254818
229541438
Hashcode test of StringBuffer:
118352462
118352462
StringBuilder Class In JavaSpecial Characters