How do I swap two string variables in Java without using a third variable, i.e. the temp variable?
String a = "one"
String b = "two"
String temp = null;
temp = a;
a = b;
b = temp;
But here there is a third variable. We need to eliminate the use of the third variable.
Do it like this without using a third variable:
String a = "one";
String b = "two";
a = a + b;
b = a.substring(0, (a.length() - b.length()));
a = a.substring(b.length());
System.out.println("a = " + a);
System.out.println("b = " + b);
// taken from this answer: https://stackoverflow.com/a/16826296/427413
String returnFirst(String x, String y) {
return x;
}
String a = "one"
String b = "two"
a = returnFirst(b, b = a); // If this is confusing try reading as a=b; b=a;
This works because the Java language guarantees (Java Language Specification, Java SE 7 Edition, section 15.12.4.2) that all arguments are evaluated from left to right (unlike some other languages, where the order of evaluation is undefined), so the execution order is:
b is evaluated in order to be passed as the first argument to the functionb = a is evaluated, and the result (the new value of b) is passed as the second argument to the functionb and ignoring its new valueatemp. The parameter x works as temp, but it looks cleaner because you define the function once and you can use it everywhere.String a="one";
String b="two";
a = a.concat("#" + b);
b = a.split("#")[0];
a = a.split("#")[1];
This will work as long as your string doesn't contain the # character in them. Feel free to use any other character instead.
You could use a possible Unicode character, like "\u001E" instead of the #.
public class SwapStringVariable {
public static void main(String[] args) {
// TODO Auto-generated method stub
String a = "test";
String b = "paper";
a = a + b;
b = a.substring(0, a.length() - b.length());
a = a.substring(b.length(), a.length());
System.out.println(a + " " + b);
}
}
String str1 = "first";
String str2 = "second";
str1 = str2+str1;
str2 = str1.substring(str2.length(),str1.length());
str1 = str1.substring(0,(str1.length() - str2.length()));
System.out.println(str1);
System.out.println(str2);
The simplest way is given below:
String a = "one";
String b = "two";
System.out.println("Before swap: " a + " " + b);
int len = a.length();
a = a + b;
b = a.substring(0, len);
a = a.substring(len);
System.out.println("After swap: " a + " " + b);
String name = "george";
String name2 = "mark";
System.out.println(name+" "+name2);
System.out.println(name.substring(name.length()) + name2 + " "+ name );
Here substring(); method returns empty string. hence , names can be appended.
Here you go. Try this:
String a = "one";
String b = "two";
//String temp=null;
int i = a.length();
a += b;
b = a.substring(0, i);
a = a.substring(i, a.length());
System.out.println(a + " " + b);
Take any value in as string in a variable. It will be swap.
Actually, the code in your question did not swap String a,b.
You should see this issue: Swap two strings in Java, by passing them to a utility function, but without returning objects or using wrapper classes
And Java is passing by value: Is Java "pass-by-reference" or "pass-by-value"?
Jj Tuibeo's solution works if you add replaceFirst() and use a regular expression:
a += b;
b = a.replaceFirst(b + "$", "");
a = a.replaceFirst("^" + b, "");
For String Method 1:
public class SwapWithoutThirdVar{
public static void main (String args[]){
String s1 ="one";
String s2 ="two";
s1= s1+s2;
s2 = s1.substring(0,(s1.length()-s2.length()));
s1 = s1.substring(s2.length());
System.out.println("s1 == "+ s1);
System.out.println("s2 == "+ s2);
}
}
Method 2:
public class SwapWithoutThirdVar
{
public static void main (String[] args) throws java.lang.Exception
{
String s1 = "one";
String s2 ="two";
s1=s2+s1;
s2=s1.replace(s2,"");
s1=s1.replace(s2,"");
System.out.println("S1 : "+s1);
System.out.println("S2 : "+s2);
}
}
For Integers
public class SwapWithoutThirdVar {
public static void main(String a[]){
int x = 10;
int y = 20;
x = x+y;
y=x-y;
x=x-y;
System.out.println("After swap:");
System.out.println("x value: "+x);
System.out.println("y value: "+y);
}
}
You can do in this way.
public static void main(String[] args) {
// TODO Auto-generated method stub
String a = "one";
String b = "two";
System.out.println(a);
System.out.println(b);
a = a+b;
b = "";
System.out.println("*************");
b = a.substring(0, 3);
a = a.substring(3, 6);
System.out.println(a);
System.out.println(b);
}
package com.core;
public class SwappingNoTemp {
public static void main(String[] args) {
String a = "java";
String b = "c";
a = a + b;
b = a.substring(0, a.length() - b.length());
a = a.substring(b.length());
System.out.println("swapping is a.." + a);
System.out.println("swapping is b.." + b);
}
}
String a = "one";//creates "one" object on heap
String b = "two";// creates "two" object on heap
System.out.printf("a is %s , b is %s%n",a,b);
a = "two";// will not create new "two" object & now a is pointing to "two" object
b = "one";// will not create new "one" object & now b is pointing to "one" object
System.out.printf("a is %s , b is %s%n",a,b);
You can also do this by using a temp variable but in a different way:
String a = "one"
String b = "two"
String temp = null;
temp=a.concat(b);
b=temp.substring(0,a.length());
a=temp.substring(a.length(),temp.length());
System.out.println("After Swapping A:"+a+"B:"+b);
For strings:
String a = "one"
String b = "two"
a = a + b;
b = a.replace(b, "");
a = a.replace(b, "");
public class ex{
public static void main(String[] args){
String s1="abc";
String s2="def";
System.out.println(s1);
System.out.println(s2);
s3=s2.replaceAll(s1,s2=s1);
System.out.println(s1);
System.out.println(s2);
}
}
