Why Does Appending an Empty String to a Substring Reduce Memory Usage in Java?

Why does appending an empty string to a substring reduce memory consumption in Java?

this.smallpart = data.substring(12,18) + "";

In Java, when you create a substring with the `substring()` method, the new substring initially holds a reference to the original string's character array if the original string is not large enough to be discarded. This can lead to higher memory usage than expected. By appending an empty string (""), a new immutable string instance is created, thus breaking the reference to the original string and optimizing memory usage.

this.smallpart = new String(data.substring(12, 18));

Causes

• Java's substring() method retains a reference to the original string for performance, leading to memory overhead.
• Not explicitly creating a new string instance can result in memory being retained longer than necessary.

Solutions

• To avoid excessive memory usage, append an empty string when creating substrings.
• Use the `String` constructor to create a new string instance if memory needs to be freed.

Mistake: Using `substring()` without appending an empty string can lead to memory retention issues.

Solution: Always append an empty string to create a new string object.

Mistake: Assuming `data = new String(data.substring(0,100))` will reduce memory usage effectively.

Solution: This technically creates a new string but may not reduce the reference to the original large string used.