Following program shows how to remove negative numbers from an array.Exampleimport java.util.ArrayList; import java.util.Iterator; import java.util.List; public class Tester {    public static void main(String[] args) {       List objArray = new ArrayList();       objArray.clear();       objArray.add(2);       objArray.add(-3);       objArray.add(4);       System.out.println("Array before removing an element "+objArray);       Iterator iterator = objArray.iterator();                while(iterator.hasNext()) {          Integer next = iterator.next();          if(next < 0) {             iterator.remove();          }       }       System.out.println("Array after removing an element"+objArray);    } }OutputArray before removing an element [ 2, -3, 4 ] Array after removing an element [ 2, 4 ]

Array of Object class can be created which can accept any type of object. During operation on such array, instanceof operator can be used.Examplepublic class Tester {    public static void main(String[] args) {       Object[] dataArray = new Object[3];       dataArray[0] = new Integer(0);       dataArray[1] = new String("1");       dataArray[2] = new Boolean(false);       for(Object data: dataArray) {          if(data instanceof Integer) {             System.out.println(((Integer) data).intValue());          }          if(data instanceof String) {             System.out.println(data);          }          if(data instanceof Boolean) {             System.out.println(((Boolean) data).booleanValue());          }       }    } }Output0 1 false

Following program is converting an ArrayList to String[];Exampleimport java.util.ArrayList; import java.util.List; public class Tester {    public static void main(String[] args) {       List names = new ArrayList();       names.add("A");       names.add("B");       names.add("C");       String[] nameArray = names.toArray(new String[names.size()]);       for(String name: nameArray) {          System.out.println(name);       }    } }OutputA B C

Following program converts a vector into a array of String.Exampleimport java.util.Vector; public class Tester {    public static void main(String[] args) {       Vector data = new Vector();       data.add("A");       data.add("B");       data.add("C");       String[] strObjects = data.toArray(new String[data.size()]);       for(String obj: strObjects) {          System.out.println(obj);       }    } }

As list.toArray() returns an Object[], it can be converted to String array by passing the String[] as parameter. See the example below.import java.util.ArrayList; import java.util.List; public class Tester { public static void main(String[] args) { List data = new ArrayList(); data.add("A"); data.add("B"); data.add("C"); //Object[] objects = data.toArray(); String[] strObjects = data.toArray(new String[0]); for(String obj: strObjects) { System.out.println(obj); } } }OutputA B C

Use String(byte[]) constructor to convert byte[] to String.Examplepublic class Tester {    public static void main(String[] args) {       String test = "I love learning Java";       byte[] bytes = test.getBytes();       String converted = new String(bytes);       System.out.println(converted);    } }OutputI love learning Java

Just split the string based on space and then iterate it. See the example below −Examplepublic class Tester {    public static void main(String[] args) {       String test = "I love learning Java";       String[] subStrings = test.split(" ");       for(String subString: subStrings) {          System.out.println(subString);       }    } }OutputI love learning Java

Following example shows how to loop through an array using a foreach loop.public class Tester {    public static void main(String[] args) {       int[] dataArray = {1, 2, 3, 4};       for(int i: dataArray) {          System.out.println(i);       }    } }

https://www.tutorialspoint.com/javaexamples/string_compare.htm

Yes, Storing password in String object is not safe for following reasons −String objects are immutable and until garbage collected, they remain in memory.String being plain text can be tracked in memory dump of the application.In log, String based password may be printed which can cause a problem.Char[] can be cleared or wiped out after the job is done.