string replace java

1public static void main(String args[]){  
2String s1="my name is khan my name is java";  
3String replaceString=s1.replace("is","was");//replaces all occurrences of "is" to "was"  
4System.out.println(replaceString);  
5}}  
6

1String str = ".............................."; 
2
3        int index = 5; 
4  
5        char ch = '|'; 
6 
7        StringBuilder string = new StringBuilder(str); 
8        string.setCharAt(index, ch); 
9
10        System.out.println(string); 

1String s1 = "my name is khan and my name is java";
2String replaceString = s1.replace("is","was");
3//replaces all occurrences of "is" to "was"
4System.out.println(replaceString);

1String a = "Cool";
2a = a.replace("o","yy");
3

1public static void main(String args[]){  
2String s1="my name is khan my name is java";  
3String replaceString=s1.replace("is","was");//replaces all occurrences of "is" to "was"  
4System.out.println(replaceString);  
5}}  

1String str = "helloslkhellodjladfjhello";
2String findStr = "hello";
3int lastIndex = 0;
4int count = 0;
5while(lastIndex != -1){
6    lastIndex = str.indexOf(findStr,lastIndex);
7    if(lastIndex != -1){
8        count ++;
9        lastIndex += findStr.length();
10    }
11}
12System.out.println(count);