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public class StringLengthTest {
	
	public static void main(String[] args){
		String str = "abcdef";
		char[] elements = str.toCharArray();
		int count=0;
		for(char c : elements){
			count++;
		}
		System.out.println(count);
	}

}

My try in Java

public class StrLen {

	public static void main(String[] args) {
		System.out.println(strlen("abcde"));
	}
		
	static int strlen(String str) {

		if (str != null) {
			for(int len = 0;; len++) {
				try {
					str.charAt(len);
				}
				catch (IndexOutOfBoundsException e) {
					return len;
				}
			}
		}
		
		return 0;
	}
}

int strlen(String a) {
if (a == null) return 0;
int i = 0;
try {
while (a.charAt(i) != -1) i++;
}
catch (IndexOutOfBoundsException e) {
return i;
}
return i;
}

/**
 * How could you make sure that thread A ,B and C run sequentially without using join method?
 * 
 * @author manoj.sharma
 * @source Barclays
 */

public class ThreadJoiningWithoutJoin {

	public static void main(String[] args) {
		final JoinTask task = new JoinTask();
		
		Thread A = new Thread(){
			public void run(){
				task.doJob(1, "JOB A DONE...");
			}
		};
		
		Thread B = new Thread(){
			public void run(){
				task.doJob(2, "JOB B DONE...");
			}
		};
		
		Thread C = new Thread(){
			public void run(){
				task.doJob(3, "JOB C DONE...");
			}
		};

		C.start();
		B.start();
		A.start();
		
	}

}

// Shared Class or Object 
class JoinTask {
	
	private int currentRank = 1;
	
	public void doJob(int rank, String msg) {
		synchronized(this) {
			while (rank != currentRank) {
				try {wait();}catch(InterruptedException ex) {ex.printStackTrace();};
			}
			System.out.println("Job:" + currentRank + " : " + msg );
			currentRank++;
			notifyAll();
		}
	}
}

It does not need to check all positions.

Check char at position 2 then 4 then 8 and so on until caught exception.

public static int len(String str){
		if(str==null)
			return 0;
		else{
			int index=2;
			try {
				while (true){
					str.charAt(index); 
					index *= 2;
				}
			} catch (IndexOutOfBoundsException e) {
				return checkSize(str,index/2,index);
			}
		}
	}

then call recursive method which returns the position of last char.

public static int checkSize(String str, int l, int r){
		if(l+1==r)
			return r;
		else {
			int index=(l+r)/2;
			try{
				str.charAt(index);
				return checkSize(str,index,r);
			}
			catch (IndexOutOfBoundsException e) {
				return checkSize(str,l,index);
			}
		}
	}

public static void main(String[] args){
		String s="string jelly";
		int l=getLength(s);
		System.out.print(l);
	}
	
	static int getLength(String s){
		char[] ch=s.toCharArray();
		int len=0;
		for(char c:ch){
			len++;
		}
		return len;
	}

public class StringTest {

	public static void main(String args[]){
		String s = new String("test213");
		try {
			int count = (Integer)getFieldValue(s, "count");
			int offset = (Integer)getFieldValue(s, "offset");
			System.out.println("Size :"+(count-offset));
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	static Object getFieldValue(String s,String fieldName) throws SecurityException, NoSuchFieldException, IllegalArgumentException, IllegalAccessException {
		Object chars = null;
		Field fieldValue = String.class.getDeclaredField(fieldName);
		fieldValue.setAccessible(true);
		chars = fieldValue.get(s);
		return chars;
	}

}

Use Reflection to get values of count and offset.

public static int getLength(String src){
		int len = 0;
		String temp= src;
		try{
			while(null != temp){
				temp = src.substring(len);
				System.out.println(temp+" : "+len);
				len++;
			}
		}catch(StringIndexOutOfBoundsException se){
			
		}
		
		return len-1;
	}

a better approach:

String input = "HelloWorld";
		System.out.println(input.lastIndexOf(""));

public class StringLength2{
static String name="BHAVANI";
static int cnt=0;
public static void main(String[] args){
while(true){
try{
if(Character.isLetter(name.charAt(cnt))){
cnt++;
}}catch(Exception E){
System.out.println("length is : " + cnt);
break;
}}}
}

String input = "abcde ";
int n = input.indexOf(' ');
System.out.println("result: " + n);

You can read bytes from String. It will return byte array. Now you can get the length of it, which is length of String.

Source code is given below :

public int getSize(String str) {
		byte[] arr = str.getBytes();
		int length = arr.length;
		System.out.println("Length = " + length);
		return length;
	}