Creating a String in Java

We know that there are two ways to create a String variable:

String str1 = "abcd";
String str2 = new String("abcd");
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So why do these two types of creation exist, and what are the differences between their representations in memory?

Here are two common interview questions.

Interview Question 1:

String a = "abcd";
String b = "abcd";
System.out.println(a == b);  // true
System.out.println(a.equals(b)); // true
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Resolution:

== and equals return true. This is because a and B refer to the same string in the method area. Therefore, the same string is created only once in the method area when it is created repeatedly.

Interview Question 2:

String c = new String("abcd");
String d = new String("abcd");
System.out.println(c == d);  // false
System.out.println(c.equals(d)); // true
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Resolution:

Equals equals equals equals equals equals equals equals equals equals equals equals equals equals equals equals equals equals equals equals equals equals equals equals equals equals equals equals equals equals equals Strings created with new are created in the JVM heap each time, so c and D correspond to two different strings in the heap.

The string created by “and new” in these two problems can be seen in the following figure.

Recommended reading

Dry goods: Free 2TB architect four-stage video tutorial

Interview: the most complete Java multithreaded interview questions and answers

Tools: Recommended an online creation flow chart, mind mapping software

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