Java 字符数组转字符串而不创建新对象

Question

When creating a String like this:

String s1 = “ABC”

the JVM will look in the String pool if "ABC" exists there and create a new object only if "ABC" doesn't exist yet.

So the usage of

String s1 = new String("ABC")

halts this behavior and will create an object every time.

Now I have a problem when converting a char array to String:

private char[] names;
...
@Override
public String toString() {
  return new String(this.names);
}

This will always create a new object. Can I convert from char array to String without creating a new object each time?

Answer 1

I know of no way to avoid creating a String object in your toString() , but you can avoid retaining these new strings (all but the first one become eligible for GC after the method execution) by explicitly calling String.intern() :

@Override
public String toString() {
    return new String(this.names).intern();
}

And you can test it by repeatedly checking myObject.toString() == myObject.toString() .

But before doing this, do yourself a favor and be aware of what you're doing . It's possible that generating a string object is the better choice, depending on your main reason for doing this.

Answer 2

If your objective is to reduce memory usage you could also consider what you typically store in char[] names and how you manipulate that member field in other code not shown in your example. It may reduce memory to switch from char[] to String .

Java 9 introduced compact strings which reduce the internal storage for Latin String versus those that need UTF16. Thus in some cases new String(this.names) uses less memory than char[] names as it stores byte[] representation of the same characters - although this incurs expense of an extra object for the String . However String may not be suitable representation for your other operations that access names especially if you need to call toCharArray() to get the original format back in order for the application to work as before.