"text" 和有什么不一样?和新的字符串(“文本")? [英] What is the difference between "text" and new String("text")?

问题描述

下面这两个语句有什么区别?

What is the difference between these two following statements?

String s = "text";

String s = new String("text");

推荐答案

new String("text");显式地创建一个新的和引用不同的 String 对象实例；String s = "text"; 可以重用 字符串常量池 中的一个实例(如果有的话).

new String("text"); explicitly creates a new and referentially distinct instance of a String object; String s = "text"; may reuse an instance from the string constant pool if one is available.

您很少会想要使用 new String(anotherString) 构造函数.来自 API:

You very rarely would ever want to use the new String(anotherString) constructor. From the API:

String(String original) :初始化一个新创建的 String 对象，使其表示与参数相同的字符序列；换句话说，新创建的字符串是参数字符串的副本.除非需要原始的显式副本，否则不需要使用此构造函数，因为字符串是不可变的.

String(String original) : Initializes a newly created String object so that it represents the same sequence of characters as the argument; in other words, the newly created string is a copy of the argument string. Unless an explicit copy of original is needed, use of this constructor is unnecessary since strings are immutable.

相关问题

• Java 字符串:String s = new String("silly);"
• 字符串是 Java 中的对象，那么为什么我们不使用new"来创建它们呢?

检查以下代码段:

    String s1 = "foobar";
    String s2 = "foobar";

    System.out.println(s1 == s2);      // true

    s2 = new String("foobar");
    System.out.println(s1 == s2);      // false
    System.out.println(s1.equals(s2)); // true

== 在两个引用类型上是一个引用标识比较.equals 的两个对象不一定是 ==.在引用类型上使用 == 通常是错误的；大多数情况下需要使用 equals 代替.

== on two reference types is a reference identity comparison. Two objects that are equals are not necessarily ==. It is usually wrong to use == on reference types; most of the time equals need to be used instead.

尽管如此，如果出于某种原因您需要创建两个 equals 而不是 == 字符串，您可以使用 newString(anotherString) 构造函数.然而，需要再次说明的是，这是非常的，而且很少是本意.

Nonetheless, if for whatever reason you need to create two equals but not == string, you can use the new String(anotherString) constructor. It needs to be said again, however, that this is very peculiar, and is rarely the intention.

• JLS 15.21.3 引用相等运算符 == 和 !=
• class Object - boolean Object(equals)
• Java String.equals 与 ==
• 如何比较 Java 中的字符串?

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