Java String replace()

The Java String class replace() method returns a string replacing all the old char or CharSequence to new char or CharSequence.

Since JDK 1.5, a new replace() method is introduced that allows us to replace a sequence of char values.

Signature

There are two types of replace() methods in Java String class.

  public String replace(char oldChar, char newChar)    public String replace(CharSequence target, CharSequence replacement)    

The second replace() method is added since JDK 1.5.

Parameters

oldChar : old character

newChar : new character

target : target sequence of characters

replacement : replacement sequence of characters

Returns

replaced string

Exception Throws

NullPointerException: if the replacement or target is equal to null.

Internal implementation

  public String replace(char oldChar, char newChar) {           if (oldChar != newChar) {               int len = value.length;               int i = -1;               char[] val = value; /* avoid getfield opcode */                   while (++i < len) {                   if (val[i] == oldChar) {                       break;                   }               }               if (i < len) {                   char buf[] = new char[len];                   for (int j = 0; j < i; j++) {                       buf[j] = val[j];                   }                   while (i < len) {                       char c = val[i];                       buf[i] = (c == oldChar) ? newChar : c;                       i++;                   }                   return new String(buf, true);               }           }           return this;       }    

  public String replace(CharSequence target, CharSequence replacement)  {          return Pattern.compile(target.toString(), Pattern.LITERAL).matcher(  this).replaceAll(Matcher.quoteReplacement(replacement.toString()));  }  