diff --git a/Java/String/Caseconvert.java b/Java/String/Caseconvert.java
new file mode 100644
index 00000000..216cc03f
--- /dev/null
+++ b/Java/String/Caseconvert.java
@@ -0,0 +1,15 @@
+import java.util.Scanner;
+
+public class Caseconvet {
+    
+
+
+
+
+    public static void main(String[] args) {
+       Scanner sc =new Scanner(System.in);
+     
+        String Str =sc.nextLine();
+        System.out.println(Str.toUpperCase());
+    }
+}
diff --git a/Java/String/LargeSTR.java b/Java/String/LargeSTR.java
new file mode 100644
index 00000000..18eeaa7d
--- /dev/null
+++ b/Java/String/LargeSTR.java
@@ -0,0 +1,14 @@
+public class LargeSTR {
+    
+
+    public static void main(String[] args) {
+        String Fruits[] = {"Nishit","Bhumika","Kapila"};
+String Largest = Fruits[0];
+for(int i=1 ;i< Fruits.length;i++){
+if(Largest.compareTo(Fruits[i]) < 0 ){
+Largest = Fruits[i];
+}
+}
+System.out.println(Largest);
+    }
+}
diff --git a/Java/String/Str.java b/Java/String/Str.java
new file mode 100644
index 00000000..7e314910
--- /dev/null
+++ b/Java/String/Str.java
@@ -0,0 +1,23 @@
+import java.util.Scanner;
+
+public class Str {
+    
+public static boolean palidrom(String name ){
+for(int i=0 ; i<name.length()/2;i++){
+int n = name.length();
+if(name.charAt(i) != name.charAt(n-i-1)  ){
+    return false;
+}
+
+}
+  return true;  
+}
+
+public static void main(String[] args) {
+Scanner sc = new Scanner(System.in);
+String name ;
+name = sc.nextLine();
+System.out.println(" The Length Of String is -->"+ name.length());
+System.out.println(palidrom(name));                    
+}
+}
\ No newline at end of file
diff --git a/Java/String/Strbuilder.java b/Java/String/Strbuilder.java
new file mode 100644
index 00000000..331d2061
--- /dev/null
+++ b/Java/String/Strbuilder.java
@@ -0,0 +1,20 @@
+public class Strbuilder {
+    
+
+public static void main(String[] args) {
+    StringBuilder sc = new StringBuilder(""); 
+for(char ch='a'; ch < 'z';ch++   ){
+sc.append(ch);
+}
+
+System.out.print(sc+ " ") ;
+}
+}
+
+// Java StringBuilder class is used to create mutable (modifiable) String. The Java StringBuilder class is same as StringBuffer class except that it is non-synchronized. It is available since JDK 1.5.
+
+/*  Important Constructors of StringBuilder class
+ Constructor	Description
+ StringBuilder()	It creates an empty String Builder with the initial capacity of 16.
+ StringBuilder(String str)	It creates a String Builder with the specified string.
+ StringBuilder(int length)	It creates an empty String Builder with the specified capacity as length.*/
\ No newline at end of file
diff --git a/Java/String/compress.java b/Java/String/compress.java
new file mode 100644
index 00000000..cd595d96
--- /dev/null
+++ b/Java/String/compress.java
@@ -0,0 +1,27 @@
+public class compress {
+    
+    public static String compressq(String str){
+        String newstr = "";
+    for(int i=0 ; i<str.length() ; i++){
+    Integer count =1;
+    while( i < str.length()-1 &&  str.charAt(1) == str.charAt(i+1) ){
+    count++;
+    i++;
+    }
+    newstr += str.charAt(i);
+    if(count > 1){
+        newstr += count.toString();
+    }
+    }
+        return newstr;
+    }
+    
+    
+    
+        public static void main(String[] args) {
+            String str = "aavv";
+    System.out.print(compressq(str));
+    
+        }
+    }
+//time Complexcity O(N)    :) #NIshit
\ No newline at end of file
diff --git a/Java/String/substring.java b/Java/String/substring.java
new file mode 100644
index 00000000..4aa43a18
--- /dev/null
+++ b/Java/String/substring.java
@@ -0,0 +1,8 @@
+public class substring {
+
+
+    public static void main(String[] args) {
+       String Str = "HelloWorld";
+       System.out.println(Str.substring(0,5) ); //Java Has a inbulid Funcation  of Substring  // 
+    }
+}
\ No newline at end of file