# String Methods

`String` is a fundamental class in Java for working with text. It provides a wide range of methods for manipulating and inspecting strings. This documentation covers some of the most frequently used methods with real-time examples.

### 1. `length()`

#### Method Signature

```java
int length()
```

#### Description

This method returns the length (the number of characters) of the `String`.

#### Example

```java
String text = "Hello, World!";
int length = text.length(); // length will be 13
```

### 2. `charAt(int index)`

#### Method Signature

```java
char charAt(int index)
```

#### Description

This method returns the character at the specified index in the `String`.

#### Example

```java
String text = "Java";
char character = text.charAt(1); // character will be 'a'
```

### 3. `substring(int beginIndex)`

#### Method Signature

```java
String substring(int beginIndex)
```

#### Description

This method returns a new `String` that is a substring of the original string starting from the specified `beginIndex`.

#### Example

```java
String text = "Hello, World!";
String substring = text.substring(7); // substring will be "World!"
```

### 4. `substring(int beginIndex, int endIndex)`

#### Method Signature

```java
String substring(int beginIndex, int endIndex)
```

#### Description

This method returns a new `String` that is a substring of the original string, starting from `beginIndex` (inclusive) and ending at `endIndex` (exclusive).

#### Example

```java
String text = "Hello, World!";
String substring = text.substring(7, 12); // substring will be "World"
```

### 5. `concat(String str)`

#### Method Signature

```java
String concat(String str)
```

#### Description

This method concatenates the specified string (`str`) to the end of the original string and returns the resulting `String`.

#### Example

```java
String text = "Hello";
String newText = text.concat(", World!"); // newText will be "Hello, World!"
```

### 6. `equals(Object obj)`

#### Method Signature

```java
boolean equals(Object obj)
```

#### Description

This method compares the content of two strings and returns `true` if they are equal, `false` otherwise.

#### Example

```java
String str1 = "Hello";
String str2 = "Hello";
boolean isEqual = str1.equals(str2); // isEqual will be true
```

### 7. `equalsIgnoreCase(String anotherString)`

#### Method Signature

```java
boolean equalsIgnoreCase(String anotherString)
```

#### Description

This method compares two strings, ignoring their case (uppercase/lowercase), and returns `true` if they are equal, `false` otherwise.

#### Example

```java
String str1 = "Hello";
String str2 = "hello";
boolean isEqual = str1.equalsIgnoreCase(str2); // isEqual will be true
```

### 8. `startsWith(String prefix)`

#### Method Signature

```java
boolean startsWith(String prefix)
```

#### Description

This method checks if the `String` starts with the specified prefix and returns `true` if it does, `false` otherwise.

#### Example

```java
String text = "Hello, World!";
boolean startsWithHello = text.startsWith("Hello"); // startsWithHello will be true
```

### 9. `endsWith(String suffix)`

#### Method Signature

```java
boolean endsWith(String suffix)
```

#### Description

This method checks if the `String` ends with the specified suffix and returns `true` if it does, `false` otherwise.

#### Example

```java
String text = "Hello, World!";
boolean endsWithWorld = text.endsWith("World!"); // endsWithWorld will be true
```

### 10. `contains(CharSequence sequence)`

#### Method Signature

```java
boolean contains(CharSequence sequence)
```

#### Description

This method checks if the `String` contains the specified sequence of characters and returns `true` if it does, `false` otherwise.

#### Example

```java
String text = "The quick brown fox";
boolean containsFox = text.contains("fox"); // containsFox will be true
```

### 11. `replace(CharSequence target, CharSequence replacement)`

#### Method Signature

```java
String replace(CharSequence target, CharSequence replacement)
```

#### Description

This method replaces all occurrences of the `target` character sequence with the `replacement` character sequence and returns the resulting `String`.

#### Example

```java
String text = "I love Java. Java is great!";
String replacedText = text.replace("Java", "Python");
// replacedText will be "I love Python. Python is great!"
```

### 12. `trim()`

#### Method Signature

```java
String trim()
```

#### Description

This method removes leading and trailing whitespace from the `String` and returns the resulting `String`.

#### Example

```java
String text = "   This is a string with whitespace.   ";
String trimmedText = text.trim();
// trimmedText will be "This is a string with whitespace."
```

### 13. `split(String regex)`

#### Method Signature

```java
String[] split(String regex)
```

#### Description

This method splits the `String` into an array of substrings based on the provided regular expression (`regex`) and returns the array.

#### Example

```java
String text = "apple,banana,cherry";
String[] fruits = text.split(",");
// fruits will be ["apple", "banana", "cherry"]
```

### 14. `toUpperCase()` and `toLowerCase()`

#### Method Signature

```java
String toUpperCase()
String toLowerCase()
```

#### Description

These methods convert all characters in the `String` to uppercase or lowercase, respectively, and return the resulting `String`.

#### Example

```java
String text = "Hello, World!";
String upperCaseText = text.toUpperCase(); // upperCaseText will be "HELLO, WORLD!"
String lowerCaseText = text.toLowerCase(); // lowerCaseText will be "hello, world!"
```

### 15. `isEmpty()`

#### Method Signature

```java
boolean isEmpty()
```

#### Description

This method checks if the `String` is empty (has a length of 0) and returns `true` if it is, `false` otherwise.

#### Example

```java
String emptyString = "";
boolean isEmpty = emptyString.isEmpty(); // isEmpty will be true
```

***

These are some of the most frequently used `String` methods in Java, along with real-time examples. Strings are essential in Java for working with text data, and understanding these methods will help you manipulate and analyze text efficiently in your Java applications.


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