Several writing methods and efficiency of Java string splicing

String splicing

The first way uses +

String s1="abc";
String s2="def";
String s3=s1+s2;

note:Using + to splice strings, the bottom layer will create a StringBuilder instance and call the append() method to splice.

Let's take a look at the performance of two + splicing strings

There are three strings s1, s3, and s3. After concatenating the three characters, it returns to the
first one:

public static String concat(String s1, String s2, String s3) {
    
    
        String result = "";
        result += s1;
        result += s2;
        result += s3;
        return result;
    }

The second

public static String concat(String s1, String s2, String s3) {
    
    
        return s1 + s2 + s3 ;
    }

Compare the performance of the two methods: if it is executed 10,000 times, the
second method is obviously better.
For the first method: three statements, each call + new StringBuilder object, then the first method requires newthree timesStringBuilder
for the second way: only newonceStringBuilder can

The second way uses String.concat()

String s1="abc";
String s2="def";
String s3=s1.concat(s3);

The underlying code is converted to byte[], and then new String(bytes,coder);
concat is faster than +

The third way to use StringBuilder.append

String s1="abc";
String s2="def";
StringBuffer s3 = new StringBuffer(s1);
s3.append(s2);

Performance comparison of three methods

StringBuilder.append(s) > String.concat(s) > +