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StringBuilder insert and append

In this chapter you will learn:

  1. How to append data to the end of a StringBuilder
  2. How to chain append methods together
  3. How to insert data to the middle of a StringBuilder
  4. Combine append and insert methods

Append data to the end

StringBuilder has the following methods to append data to the end of a StringBuilder.
  • StringBuilder append(boolean b)
  • StringBuilder append(char c)
  • StringBuilder append(char[] str)
  • StringBuilder append(char[] str, int offset, int len)
  • StringBuilder append(CharSequence s)
  • StringBuilder append(CharSequence s, int start, int end)
  • StringBuilder append(double d)
  • StringBuilder append(float f)
  • StringBuilder append(int i)
  • StringBuilder append(long lng)
  • StringBuilder append(Object obj)
  • StringBuilder append(String str)
  • StringBuilder append(StringBuffer sb)
  • StringBuilder appendCodePoint(int codePoint)
public class Main {
  public static void main(String[] argv) {
    StringBuilder sb = new StringBuilder();
    sb.append("java2s.com");
    sb.append(123);//from  j  a  v  a 2  s.c  o  m
    sb.append(1.23);
    sb.append(true);
    System.out.println(sb.toString());

  }
}

The output:

Chain append methods together

Each append methods from StringBuilder return an instance of current StringBuilder. We can chain the append methods together.

public class Main {
/*  ja v  a2 s.com*/
  public static void main(String[] argv) {

    String s1 = "Hello" + ", " + "World";
    System.out.println(s1);

    // Build a StringBuilder, and append some things to it.
    StringBuilder sb2 = new StringBuilder();
    sb2.append("Hello");
    sb2.append(',');
    sb2.append(' ');
    sb2.append("World");

    StringBuilder sb3 = new StringBuilder().append("Hello").append(',').append(' ').append("World");
    System.out.println(sb3.toString());
  }
}

The output:

Insert data to the middle of a StringBuilder

With the following insert methods from StringBuilder we can insert value to the middle of a StringBuilder.

  • StringBuilder insert(int offset, boolean b)
  • StringBuilder insert(int offset, char c)
  • StringBuilder insert(int offset, char[] str)
  • StringBuilder insert(int index, char[] str, int offset, int len)
  • StringBuilder insert(int dstOffset, CharSequence s)
  • StringBuilder insert(int dstOffset, CharSequence s, int start, int end)
  • StringBuilder insert(int offset, double d)
  • StringBuilder insert(int offset, float f)
  • StringBuilder insert(int offset, int i)
  • StringBuilder insert(int offset, long l)
  • StringBuilder insert(int offset, Object obj)
  • StringBuilder insert(int offset, String str)

The following code inserts three lines of string to the StringBuilder. The new line escape string \n is used.

public class Main {
  public static void main(String[] a) {
    StringBuilder builder = new StringBuilder("Line 1\n");
/* j  av a  2s.  c  o m*/
    builder.append("Line 3\n");

    String lineToInsert = "Line 2\n";
    
    builder.insert(0, lineToInsert);

    System.out.println(builder.toString());

  }
}

Output:

Combine append and insert methods

public class Main {
  public static void main(String[] argv) {
    StringBuilder sb = new StringBuilder();
    sb.append("java2s.com");
    sb.append(123);/* jav a  2s  .  c o m*/
    sb.append(1.23);
    sb.append(true);
    
    
    sb.insert(4,"JAVA2S.COM");
    System.out.println(sb.toString());

  }
}

The output:

Next chapter...

What you will learn in the next chapter:

  1. How to get the length for a StringBuilder
  2. How to get the capacity for a StringBuilder
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