String in java-2

1]write a simple string program to take from a user.
  import java.util.*;  
  class UserInputDemo1  
  {  
    public static void main(String[] args)  
      {  
      Scanner sc= new Scanner(System.in);
      System.out.print("Enter a string: ");  
      String str= sc.nextLine();              
      System.out.print("You have entered: "+str);             
     }  
 }  

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2]how do you concatenate two strings in java?
    concat()method
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3] how do you find the length of the string in java explain with an example.
  Use inbuilt length() method
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4]how do you compare two strings in java
     Using == operator
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5]write a program to find the length of the string” refrigerator”.
  class  main
    {  
      public static void main(String[] args)  
        {   
        String s = “refrigerator”;             
        System.out.print("string lenght: "+s.length());             
        }  
    }  

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6] write a program to check if the letter ‘e’ is present in the word ‘Umbrella’.
  class  main
  {  
    public static void main(String[] args)  
    {   
      String s = “Umbrella”;        
        if(word.contains(“e”))
        {     
        System.out.print("It is present”);         
        }    
        else
        {
        System.out.print("It is not  present”); 
        }
    }  
  }  

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7]write a program to delete all consonants from the string “Hello, have a good day”.

public class Main {
  public static void main(String[] args) {
    String str = "Hello, have a good day";
    String vowels = ('a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U'));
    StringBuilder sb = new StringBuilder();

    for (int i = 0; i < str.length(); i++) {
      if (vowels.contains(str.charAt(i))) {
        sb.append(str.charAt(i));
      }
    }

    System.out.println(sb.toString());
  }
}