Comparison of equals and == in Java

Let's take a look at such a topic first. Suppose there is the following code. The statement that returns false in the following options is?

String s = "hello";
String t = “hello”;
char c [ ] = {'h','e','l','l','o'};
s.equals (t);    //A
t.equals (c);    //B
s==t;    //C
t.equals (new String ("hello"));    //D

Before publishing the answer, let's take a few knowledge points.

1. Java data types are divided into:

• basic data type
• reference data type 

2. For "=="

• Used to compare basic data types with each other. Compare the two values ​​for equality.
• Used to compare reference data types with each other. Compare whether the two addresses are equal.
• Cannot be used for primitive and reference comparisons.

3. For "equals"

• Cannot be used for primitive data type comparison (because this is a method, inherited from object).
• It is used to compare objects, and compare whether the reference addresses of the two are the same.

4. Special circumstances

• Numeric primitives and numeric classes have autoboxing and auto-unboxing .
• Strings exist as constants, and if multiple string variables have the same value, they point to the same address.
• There will be automatic type conversion for numeric types .

 

At this point, the answer is very clear, choose B. 

 

 

Author: Xinxin Xin, published in   Blog Park

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