exemplos de metodos em java 1.java

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public class Main
{
	public static void main(String[] args) {
	   String mensa = "ola mundo! acabou o carnaval " + (10+20);
	   System.out.println(mensa);
	   System.out.println("tamanho da mensagem " + mensa.length());
	   System.out.println("em maiucula = " + mensa.toUpperCase());
	   System.out.println("em miniscula = " + mensa.toLowerCase());
	   System.out.println("substitua mundo : " + mensa.replace("mundo","world"));
	   System.out.println("qual a posição da letra c = " + mensa.indexOf('c'));
	   System.out.println("na posição 10 temos : " + mensa.charAt(10));
	   System.out.println("extraindo uma parte : " + mensa.substring(3,10));
	   }
}