java - String.isEmpty() 和 String.equals (""之间的区别)

Question

我创建了一个“颜色选择器”，其中包含用户定义 rgb 值的三个文本框。
要检查输入的值是否正确(仅 0-255 之间的数字)，我使用以下内容:

public Color getColor() {
    if (tfRed.getText().equals("") || tfGreen.getText().equals("") || tfBlue.getText().equals("")) {
                return new Color(0, 0, 0, 0);
    } else {
        if (tfRed.getText().matches("\\d+") && tfGreen.getText().matches("\\d+") && tfBlue.getText().matches("\\d+")) {
            // ...
        } else {
            return new Color(0, 0, 0, 0);
        }
    }
}

我要问的是:使用 String.isEmpty() 更好吗？我从来没有找到令人满意的答案，我一直想知道是否有任何区别。

Answer 1

我认为 isEmpty() 效率更高一些。然而，智能编译器可能会优化 equals("") 调用。来自 OpenJDK source :

  671     public boolean isEmpty() {
  672         return count == 0;
  673     }

 1013     public boolean equals(Object anObject) {
 1014         if (this == anObject) {
 1015             return true;
 1016         }
 1017         if (anObject instanceof String) {
 1018             String anotherString = (String)anObject;
 1019             int n = count;
 1020             if (n == anotherString.count) {
 1021                 char v1[] = value;
 1022                 char v2[] = anotherString.value;
 1023                 int i = offset;
 1024                 int j = anotherString.offset;
 1025                 while (n-- != 0) {
 1026                     if (v1[i++] != v2[j++])
 1027                         return false;
 1028                 }
 1029                 return true;
 1030             }
 1031         }
 1032         return false;
 1033     }

还有 answer here关于是否使用 str.isEmpty() 或 "".equals(str) 是正确的:

The main benefit of "".equals(s) is you don't need the null check (equals will check its argument and return false if it's null), which you seem to not care about. If you're not worried about s being null (or are otherwise checking for it), I would definitely use s.isEmpty(); it shows exactly what you're checking, you care whether or not s is empty, not whether it equals the empty string