StringBuilder vs String concatenation in toString() in Java

In Java, you can use either a StringBuilder or string concatenation to create a string representation of an object.

Using StringBuilder is generally more efficient than using string concatenation, because StringBuilder is designed specifically for concatenating strings. When you use string concatenation, the Java compiler creates a new String object each time you concatenate two strings, which can be inefficient if you are concatenating many strings.

Here is an example of how to use StringBuilder to create a string representation of an object:

public class MyObject {
    private int x;
    private int y;

    public MyObject(int x, int y) {
        this.x = x;
        this.y = y;
    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append("MyObject[x=").append(x).append(",y=").append(y).append("]");
        return sb.toString();
    }
}

In this example, the toString method uses a StringBuilder to create a string representation of the MyObject object.

Here is an example of how to use string concatenation to create a string representation of the same object:

public class MyObject {
    private int x;
    private int y;

    public MyObject(int x, int y) {
        this.x = x;
        this.y = y;
    }

    @Override
    public String toString() {
        return "MyObject[x=" + x + ",y=" + y + "]";
    }
}

I hope this helps. Let me know if you have any questions.