Insert string in beginning of another string
JavaStringJava Problem Overview
How to insert a string enclosed with double quotes in the beginning of the StringBuilder and String?
Eg:
StringBuilder _sb = new StringBuilder("Sam");
I need to insert the string "Hello" to the beginning of "Sam" and O/p is "Hello Sam".
String _s = "Jam";
I need to insert the string "Hello" to the beginning of "Jam" and O/p is "Hello Jam".
How to achieve this?
Java Solutions
Solution 1 - Java
The first case is done using the insert()
method:
_sb.insert(0, "Hello ");
The latter case can be done using the overloaded + operator on Strings. This uses a StringBuilder behind the scenes:
String s2 = "Hello " + _s;
Solution 2 - Java
Other answers explain how to insert a string at the beginning of another String
or StringBuilder
(or StringBuffer
).
However, strictly speaking, you cannot insert a string into the beginning of another one. Strings in Java are immutable1.
When you write:
String s = "Jam";
s = "Hello " + s;
you are actually causing a new String
object to be created that is the concatenation of "Hello " and "Jam". You are not actually inserting characters into an existing String
object at all.
1 - It is technically possible to use reflection to break abstraction on String
objects and mutate them ... even though they are immutable by design. But it is a really bad idea to do this. Unless you know that a String
object was created explicitly via new String(...)
it could be shared, or it could share internal state with other String
objects. Finally, the JVM spec clearly states that the behavior of code that uses reflection to change a final
is undefined. Mutation of String
objects is dangerous.
Solution 3 - Java
Sure, use StringBuilder.insert()
:
_sb.insert(0, _s);
Solution 4 - Java
private static void appendZeroAtStart() {
String strObj = "11";
int maxLegth = 5;
StringBuilder sb = new StringBuilder(strObj);
if (sb.length() <= maxLegth) {
while (sb.length() < maxLegth) {
sb.insert(0, '0');
}
} else {
System.out.println("error");
}
System.out.println("result: " + sb);
}
Solution 5 - Java
You can add a string at the front of an already existing one. for example, if I have a name string name
, I can add another string name2
by using:
name = name2 + name;
Don't know if this is helpful or not, but it works. No need to use a string builder.
Solution 6 - Java
import java.lang.StringBuilder;
public class Program {
public static void main(String[] args) {
// Create a new StringBuilder.
StringBuilder builder = new StringBuilder();
// Loop and append values.
for (int i = 0; i < 5; i++) {
builder.append("abc ");
}
// Convert to string.
String result = builder.toString();
// Print result.
System.out.println(result);
}
}
Solution 7 - Java
It is better if you find quotation marks by using the indexof()
method and then add a string behind that index.
string s="hai";
int s=s.indexof(""");