Difference between isEmpty() and isBlank() Method

问题:

Java 11 has added A new instance method isBlank() to java.lang.String class.

What's the basic difference between the existing isEmpty and newly added isBlank() method?

回答1:

isEmpty()

The java string isEmpty() method checks if this string is empty. It returns true, if the length of the string is 0 otherwise false e.g.

System.out.println("".isEmpty()); // Prints - True
System.out.println(" ".isEmpty()); //Prints - False 

Java 11 - isBlank()

The new instance method java.lang.String.isBlank() returns true if the string is empty or contains only white space, where whitespace is defined as any codepoint that returns true when passed to Character#isWhitespace(int).

boolean blank = string.isBlank();

---

Before Java 11

boolean blank = string.trim().isEmpty();

After Java 11

boolean blank = string.isBlank();

回答2:

Java 11 added has new method called .isBlank() in String class

1. isBlank() method is equal to str.trim().isEmpty() in earlier to java 11 versions
2. isEmpty() : Returns true if, and only if, length() is 0

This is the internal implementation of isBlank() method in String class of java 11

public boolean isBlank() {
    return indexOfNonWhitespace() == length();
}

private int indexOfNonWhitespace() {
    if (isLatin1()) {
        return StringLatin1.indexOfNonWhitespace(value);
    } else {
        return StringUTF16.indexOfNonWhitespace(value);
    }
}